ingles instrumental eletroeletronica2
Post on 07-Apr-2018
236 Views
Preview:
TRANSCRIPT
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 131
True History of the Transistor httpwwwbncombrradios-antigossemicondhtmThe transistor was invented in the Beel Telephone Laboratories in December 1947 (not 1948 as is oftensaid) by Bardeen and BrattainDiscovered so to speak (since they were looking for a solid state device equivalent to the vacuum tube)accidentally during studies of surfaces around a point-contact diodeThe transistors were therefore of type point-contact and there is evidence that Shockley the theorist whoheaded the research was pissed because the device was not what I was looking for At the time he waslooking for a semiconductor amplifier similar to what we now call junction FETThe name transistor was derived from their intrinsic properties transfer resistor in English (transfer resistor) Bell Labs kept the discovery secret until June 1948 (hence the confusion with the dates of discovery)With a estrodosa publicity they announced their findings publicly but few people realized thesignificance and importance of the publication despite having left the front pages of newspapersAlthough it was a great scientific achievement the transistor not reached immediately the commercialsupremacy The difficulties of manufacturing added to the high price of germanium a rare element keptthe price too high The best transistors costing $ 8 a time when the price of a valve was only 75 centsShochley ignored the point-contact transistor and continued his research in other directions He reorientedhis ideas and developed the theory of transistor junctionIn July 1951 Bell announced the creation of this device In September 1951 they promote a symposiumand are willing to license the new technology of both types of transistors to any company that was willingto pay $ 2500000This was the beginning of the industrialization of the transistorMany firms withdrew the notice of license Former manufacturers of vacuum tubes such as RCARaytheon GE and industrial leaders in the market like Texas and TransitronMany started the production of point-contact transistor which at that time worked better in highfrequency than the types of joint However the junction transistor becomes faster far superior in
performance and is simpler and easier to manufactureThe point-contact transistor was made obsolete by about 1953 in America and later in EnglandOnly a few thousand were manufactured between 120 types many Americans (not including thesenumbers trial versions)
The first junction transistor manufactured commercially was primitive compared to modern devices witha maximum voltage between collector-emitter of 6 volts and a maximum current of a few milliamps
Particularly notable was the Raytheon CK722 transistor 1953 the first device solid state electronic mass
produced available to the amateur builder Various types of transistors have been developed increasing
the frequency response by reducing noise levels and increasing its power capacity
In England two companies have maintained research labs not so early as in America Standard
Telephones and Cables (STC) and General Electric Company of England GEC (no telaccedilatildeo with the
American GE)
Research was conducted in France and Germany without trade effects
In 1950 a shark comes in this small pond the Dutch PHILIPS by Mullard its English subsidiary with a
complete plan to industrialize the transistor
The goal was to dominate the Philips 95 of the European market reaching this goal in few years The
series OC transistor dominated Europe for over 20 years
The former were made of germanium transistors a semiconductor metal but soon found that the silicon
offered a number of advantages over germanium The silicon was more difficult to refine because of its
high melting point but in 1955 the first silicon transistor was already sold
Texas Instruments was one of the companies that took part in the initial development of this technology
by launching a series of devices known at the time by the letters 900 and 2s
The big turnaround came in 1954 when Gordon Teal perfected a junction transistor made of silicon
The silicon instead of germanium a mineral is abundant only losing in the oxygen availability This fact
coupled with the improvement of production techniques have significantly decreased the price of the
transistor This enabled him to popularize and would cause a revolution in the computer industry That
only such a revolution would be repeated with the creation and refinement of integrated circuits
Major innovations in the field of semiconductors
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 231
INNOVATION LABORATORY YEAR
POINT OF CONTACT TRANSISTOR Bell Labs-Western Electric 1947
CULTIVATION IN SINGLE CRYSTAL Western Electric 1950
ZONE REFINED Western Electric 1950
TRANSISTOR JUNCTION CULTURED Western Electric 1951
SILICON TRANSISTOR Texas Instruments 1954
MASK OF OXIDE AND DIFFUSION Western Electric 1955
PLANAR TRANSISTOR Fairchild 1960
INTEGRATED CIRCUITTexas Instruments
Fairchild 1961
GUNN DIODE IBM 1963
Resistance
The electrical resistance of a circuit component or device isdefined as the ratio of the voltage applied to the electric current whichflows through it
If the resistance is constant over a considerable range of voltage then
Ohms law I = VR can be used to predict the behavior of the material
Although the definition above involves DC current and voltage the same
definition holds for the AC application of resistors
Whether or not a material obeys Ohms law its resistance can be described interms of its bulk resistivity The resistivity and thus the resistance is temperaturedependent Over sizable ranges of temperature this temperature dependence can be
predicted from a temperature coefficient of resistance
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 331
Resistivity and Conductivity
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected to
depend upon the material out of which the wire is made Experimentally thedependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a giventemperature to calculate the resistance of a wire of given geometry
The inverse of resistivity is called conductivity There are contexts where theuse of conductivity is more convenient
Electrical conductivity = σ = 1ρ
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 431
Resistor Combinations
The combination rules for any number of resistors in series or parallel can bederived with the use of Ohms Law the voltage law and the current law
Resistivity Calculation
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected todepend upon the material out of which the wire is made (resistivity)
Experimentally the dependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
Resistance = resistivity x lengtharea
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 531
For a wire of length L = m = ft
and area A = cm2
corresponding to radius r = cm
and diameter inches for common wire gauge comparison
with resistivity = ρ = x 10^ ohm meters
will have resistance R = ohms
Enter data and then click on the quantity you wish to calculate in the activeformula above Unspecified parameters will default to values typical of 10 metersof 12 copper wire Upon changes the values will not be forced to be consistentuntil you click on the quantity you wish to calculate
Commonly used US wire
gauges
for copper wire
AW
G
Diamet
er
(inches)
Typical use
10 01019 Electric range
12 00808Household
circuit
14 00640 Switch leads
Resistivities of some metals
in ohm-m(x 10-8) at 20degC
Aluminu
m265 Gold 224
Copper172
4Silver 159
Iron 971
Platinu
m 106
Nichrom
e100
Tungst
en565
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a given
temperature to calculate the resistance of a wire of given geometry
thornyuml thornyuml
thornyuml
thornyuml
thornyuml
thornyuml thornyuml
thornyuml
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 631
Resistor-Transistor Logic
Consider the most basic transistor circuit such as the one shown to the left We will only be applying one of two voltages to the input I 0 volts (logic 0) or +V volts (logic 1) The
exact voltage used as +V depends on the circuit design parameters in RTL integrated circuitsthe usual voltage is +36v Well assume an ordinary NPN transistor here with a reasonable dccurrent gain an emitter-base forward voltage of 065 volt and a collector-emitter saturationvoltage no higher than 03 volt In standard RTL ICs the base resistor is 470 and thecollector resistor is 640
When the input voltage is zero volts (actually anything under 05 volt) there is no forward bias to the emitter-base junction and the transistor does not conduct Therefore no currentflows through the collector resistor and the output voltage is +V volts Hence a logic 0 inputresults in a logic 1 output
When the input voltage is +V volts the transistors emitter-base junction will clearly beforward biased For those who like the mathematics well assume a similar output circuitconnected to this input Thus well have a voltage of 36 - 065 = 295 volts applied across aseries combination of a 640 output resistor and a 470 input resistor This gives us a basecurrent of
295v 1110 = 00026576577 amperes = 266 ma
RTL is a relatively old technology and the transistors used in RTL ICs have a dc forwardcurrent gain of around 30 If we assume a current gain of 30 266 ma base current will
support a maximum of 798 ma collector current However if we drop all but 03 volts acrossthe 640 collector resistor it will carry 33640 = 51 ma Therefore this transistor is indeedfully saturated it is turned on as hard as it can be
With a logic 1 input then this circuit produces a logic 0 output We have already seen thata logic 0 input will produce a logic 1 output Hence this is a basic inverter circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 231
INNOVATION LABORATORY YEAR
POINT OF CONTACT TRANSISTOR Bell Labs-Western Electric 1947
CULTIVATION IN SINGLE CRYSTAL Western Electric 1950
ZONE REFINED Western Electric 1950
TRANSISTOR JUNCTION CULTURED Western Electric 1951
SILICON TRANSISTOR Texas Instruments 1954
MASK OF OXIDE AND DIFFUSION Western Electric 1955
PLANAR TRANSISTOR Fairchild 1960
INTEGRATED CIRCUITTexas Instruments
Fairchild 1961
GUNN DIODE IBM 1963
Resistance
The electrical resistance of a circuit component or device isdefined as the ratio of the voltage applied to the electric current whichflows through it
If the resistance is constant over a considerable range of voltage then
Ohms law I = VR can be used to predict the behavior of the material
Although the definition above involves DC current and voltage the same
definition holds for the AC application of resistors
Whether or not a material obeys Ohms law its resistance can be described interms of its bulk resistivity The resistivity and thus the resistance is temperaturedependent Over sizable ranges of temperature this temperature dependence can be
predicted from a temperature coefficient of resistance
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 331
Resistivity and Conductivity
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected to
depend upon the material out of which the wire is made Experimentally thedependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a giventemperature to calculate the resistance of a wire of given geometry
The inverse of resistivity is called conductivity There are contexts where theuse of conductivity is more convenient
Electrical conductivity = σ = 1ρ
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 431
Resistor Combinations
The combination rules for any number of resistors in series or parallel can bederived with the use of Ohms Law the voltage law and the current law
Resistivity Calculation
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected todepend upon the material out of which the wire is made (resistivity)
Experimentally the dependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
Resistance = resistivity x lengtharea
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 531
For a wire of length L = m = ft
and area A = cm2
corresponding to radius r = cm
and diameter inches for common wire gauge comparison
with resistivity = ρ = x 10^ ohm meters
will have resistance R = ohms
Enter data and then click on the quantity you wish to calculate in the activeformula above Unspecified parameters will default to values typical of 10 metersof 12 copper wire Upon changes the values will not be forced to be consistentuntil you click on the quantity you wish to calculate
Commonly used US wire
gauges
for copper wire
AW
G
Diamet
er
(inches)
Typical use
10 01019 Electric range
12 00808Household
circuit
14 00640 Switch leads
Resistivities of some metals
in ohm-m(x 10-8) at 20degC
Aluminu
m265 Gold 224
Copper172
4Silver 159
Iron 971
Platinu
m 106
Nichrom
e100
Tungst
en565
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a given
temperature to calculate the resistance of a wire of given geometry
thornyuml thornyuml
thornyuml
thornyuml
thornyuml
thornyuml thornyuml
thornyuml
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 631
Resistor-Transistor Logic
Consider the most basic transistor circuit such as the one shown to the left We will only be applying one of two voltages to the input I 0 volts (logic 0) or +V volts (logic 1) The
exact voltage used as +V depends on the circuit design parameters in RTL integrated circuitsthe usual voltage is +36v Well assume an ordinary NPN transistor here with a reasonable dccurrent gain an emitter-base forward voltage of 065 volt and a collector-emitter saturationvoltage no higher than 03 volt In standard RTL ICs the base resistor is 470 and thecollector resistor is 640
When the input voltage is zero volts (actually anything under 05 volt) there is no forward bias to the emitter-base junction and the transistor does not conduct Therefore no currentflows through the collector resistor and the output voltage is +V volts Hence a logic 0 inputresults in a logic 1 output
When the input voltage is +V volts the transistors emitter-base junction will clearly beforward biased For those who like the mathematics well assume a similar output circuitconnected to this input Thus well have a voltage of 36 - 065 = 295 volts applied across aseries combination of a 640 output resistor and a 470 input resistor This gives us a basecurrent of
295v 1110 = 00026576577 amperes = 266 ma
RTL is a relatively old technology and the transistors used in RTL ICs have a dc forwardcurrent gain of around 30 If we assume a current gain of 30 266 ma base current will
support a maximum of 798 ma collector current However if we drop all but 03 volts acrossthe 640 collector resistor it will carry 33640 = 51 ma Therefore this transistor is indeedfully saturated it is turned on as hard as it can be
With a logic 1 input then this circuit produces a logic 0 output We have already seen thata logic 0 input will produce a logic 1 output Hence this is a basic inverter circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 331
Resistivity and Conductivity
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected to
depend upon the material out of which the wire is made Experimentally thedependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a giventemperature to calculate the resistance of a wire of given geometry
The inverse of resistivity is called conductivity There are contexts where theuse of conductivity is more convenient
Electrical conductivity = σ = 1ρ
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 431
Resistor Combinations
The combination rules for any number of resistors in series or parallel can bederived with the use of Ohms Law the voltage law and the current law
Resistivity Calculation
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected todepend upon the material out of which the wire is made (resistivity)
Experimentally the dependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
Resistance = resistivity x lengtharea
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 531
For a wire of length L = m = ft
and area A = cm2
corresponding to radius r = cm
and diameter inches for common wire gauge comparison
with resistivity = ρ = x 10^ ohm meters
will have resistance R = ohms
Enter data and then click on the quantity you wish to calculate in the activeformula above Unspecified parameters will default to values typical of 10 metersof 12 copper wire Upon changes the values will not be forced to be consistentuntil you click on the quantity you wish to calculate
Commonly used US wire
gauges
for copper wire
AW
G
Diamet
er
(inches)
Typical use
10 01019 Electric range
12 00808Household
circuit
14 00640 Switch leads
Resistivities of some metals
in ohm-m(x 10-8) at 20degC
Aluminu
m265 Gold 224
Copper172
4Silver 159
Iron 971
Platinu
m 106
Nichrom
e100
Tungst
en565
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a given
temperature to calculate the resistance of a wire of given geometry
thornyuml thornyuml
thornyuml
thornyuml
thornyuml
thornyuml thornyuml
thornyuml
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 631
Resistor-Transistor Logic
Consider the most basic transistor circuit such as the one shown to the left We will only be applying one of two voltages to the input I 0 volts (logic 0) or +V volts (logic 1) The
exact voltage used as +V depends on the circuit design parameters in RTL integrated circuitsthe usual voltage is +36v Well assume an ordinary NPN transistor here with a reasonable dccurrent gain an emitter-base forward voltage of 065 volt and a collector-emitter saturationvoltage no higher than 03 volt In standard RTL ICs the base resistor is 470 and thecollector resistor is 640
When the input voltage is zero volts (actually anything under 05 volt) there is no forward bias to the emitter-base junction and the transistor does not conduct Therefore no currentflows through the collector resistor and the output voltage is +V volts Hence a logic 0 inputresults in a logic 1 output
When the input voltage is +V volts the transistors emitter-base junction will clearly beforward biased For those who like the mathematics well assume a similar output circuitconnected to this input Thus well have a voltage of 36 - 065 = 295 volts applied across aseries combination of a 640 output resistor and a 470 input resistor This gives us a basecurrent of
295v 1110 = 00026576577 amperes = 266 ma
RTL is a relatively old technology and the transistors used in RTL ICs have a dc forwardcurrent gain of around 30 If we assume a current gain of 30 266 ma base current will
support a maximum of 798 ma collector current However if we drop all but 03 volts acrossthe 640 collector resistor it will carry 33640 = 51 ma Therefore this transistor is indeedfully saturated it is turned on as hard as it can be
With a logic 1 input then this circuit produces a logic 0 output We have already seen thata logic 0 input will produce a logic 1 output Hence this is a basic inverter circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 431
Resistor Combinations
The combination rules for any number of resistors in series or parallel can bederived with the use of Ohms Law the voltage law and the current law
Resistivity Calculation
The electrical resistance of a wire would be expected to be greater for a longer wire less for a wire of larger cross sectional area and would be expected todepend upon the material out of which the wire is made (resistivity)
Experimentally the dependence upon these properties is a straightforward one for a wide range of conditions and the resistance of a wire can be expressed as
Resistance = resistivity x lengtharea
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 531
For a wire of length L = m = ft
and area A = cm2
corresponding to radius r = cm
and diameter inches for common wire gauge comparison
with resistivity = ρ = x 10^ ohm meters
will have resistance R = ohms
Enter data and then click on the quantity you wish to calculate in the activeformula above Unspecified parameters will default to values typical of 10 metersof 12 copper wire Upon changes the values will not be forced to be consistentuntil you click on the quantity you wish to calculate
Commonly used US wire
gauges
for copper wire
AW
G
Diamet
er
(inches)
Typical use
10 01019 Electric range
12 00808Household
circuit
14 00640 Switch leads
Resistivities of some metals
in ohm-m(x 10-8) at 20degC
Aluminu
m265 Gold 224
Copper172
4Silver 159
Iron 971
Platinu
m 106
Nichrom
e100
Tungst
en565
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a given
temperature to calculate the resistance of a wire of given geometry
thornyuml thornyuml
thornyuml
thornyuml
thornyuml
thornyuml thornyuml
thornyuml
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 631
Resistor-Transistor Logic
Consider the most basic transistor circuit such as the one shown to the left We will only be applying one of two voltages to the input I 0 volts (logic 0) or +V volts (logic 1) The
exact voltage used as +V depends on the circuit design parameters in RTL integrated circuitsthe usual voltage is +36v Well assume an ordinary NPN transistor here with a reasonable dccurrent gain an emitter-base forward voltage of 065 volt and a collector-emitter saturationvoltage no higher than 03 volt In standard RTL ICs the base resistor is 470 and thecollector resistor is 640
When the input voltage is zero volts (actually anything under 05 volt) there is no forward bias to the emitter-base junction and the transistor does not conduct Therefore no currentflows through the collector resistor and the output voltage is +V volts Hence a logic 0 inputresults in a logic 1 output
When the input voltage is +V volts the transistors emitter-base junction will clearly beforward biased For those who like the mathematics well assume a similar output circuitconnected to this input Thus well have a voltage of 36 - 065 = 295 volts applied across aseries combination of a 640 output resistor and a 470 input resistor This gives us a basecurrent of
295v 1110 = 00026576577 amperes = 266 ma
RTL is a relatively old technology and the transistors used in RTL ICs have a dc forwardcurrent gain of around 30 If we assume a current gain of 30 266 ma base current will
support a maximum of 798 ma collector current However if we drop all but 03 volts acrossthe 640 collector resistor it will carry 33640 = 51 ma Therefore this transistor is indeedfully saturated it is turned on as hard as it can be
With a logic 1 input then this circuit produces a logic 0 output We have already seen thata logic 0 input will produce a logic 1 output Hence this is a basic inverter circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 531
For a wire of length L = m = ft
and area A = cm2
corresponding to radius r = cm
and diameter inches for common wire gauge comparison
with resistivity = ρ = x 10^ ohm meters
will have resistance R = ohms
Enter data and then click on the quantity you wish to calculate in the activeformula above Unspecified parameters will default to values typical of 10 metersof 12 copper wire Upon changes the values will not be forced to be consistentuntil you click on the quantity you wish to calculate
Commonly used US wire
gauges
for copper wire
AW
G
Diamet
er
(inches)
Typical use
10 01019 Electric range
12 00808Household
circuit
14 00640 Switch leads
Resistivities of some metals
in ohm-m(x 10-8) at 20degC
Aluminu
m265 Gold 224
Copper172
4Silver 159
Iron 971
Platinu
m 106
Nichrom
e100
Tungst
en565
The factor in the resistance which takes into account the nature of the materialis the resistivity Although it is temperature dependent it can be used at a given
temperature to calculate the resistance of a wire of given geometry
thornyuml thornyuml
thornyuml
thornyuml
thornyuml
thornyuml thornyuml
thornyuml
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 631
Resistor-Transistor Logic
Consider the most basic transistor circuit such as the one shown to the left We will only be applying one of two voltages to the input I 0 volts (logic 0) or +V volts (logic 1) The
exact voltage used as +V depends on the circuit design parameters in RTL integrated circuitsthe usual voltage is +36v Well assume an ordinary NPN transistor here with a reasonable dccurrent gain an emitter-base forward voltage of 065 volt and a collector-emitter saturationvoltage no higher than 03 volt In standard RTL ICs the base resistor is 470 and thecollector resistor is 640
When the input voltage is zero volts (actually anything under 05 volt) there is no forward bias to the emitter-base junction and the transistor does not conduct Therefore no currentflows through the collector resistor and the output voltage is +V volts Hence a logic 0 inputresults in a logic 1 output
When the input voltage is +V volts the transistors emitter-base junction will clearly beforward biased For those who like the mathematics well assume a similar output circuitconnected to this input Thus well have a voltage of 36 - 065 = 295 volts applied across aseries combination of a 640 output resistor and a 470 input resistor This gives us a basecurrent of
295v 1110 = 00026576577 amperes = 266 ma
RTL is a relatively old technology and the transistors used in RTL ICs have a dc forwardcurrent gain of around 30 If we assume a current gain of 30 266 ma base current will
support a maximum of 798 ma collector current However if we drop all but 03 volts acrossthe 640 collector resistor it will carry 33640 = 51 ma Therefore this transistor is indeedfully saturated it is turned on as hard as it can be
With a logic 1 input then this circuit produces a logic 0 output We have already seen thata logic 0 input will produce a logic 1 output Hence this is a basic inverter circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 631
Resistor-Transistor Logic
Consider the most basic transistor circuit such as the one shown to the left We will only be applying one of two voltages to the input I 0 volts (logic 0) or +V volts (logic 1) The
exact voltage used as +V depends on the circuit design parameters in RTL integrated circuitsthe usual voltage is +36v Well assume an ordinary NPN transistor here with a reasonable dccurrent gain an emitter-base forward voltage of 065 volt and a collector-emitter saturationvoltage no higher than 03 volt In standard RTL ICs the base resistor is 470 and thecollector resistor is 640
When the input voltage is zero volts (actually anything under 05 volt) there is no forward bias to the emitter-base junction and the transistor does not conduct Therefore no currentflows through the collector resistor and the output voltage is +V volts Hence a logic 0 inputresults in a logic 1 output
When the input voltage is +V volts the transistors emitter-base junction will clearly beforward biased For those who like the mathematics well assume a similar output circuitconnected to this input Thus well have a voltage of 36 - 065 = 295 volts applied across aseries combination of a 640 output resistor and a 470 input resistor This gives us a basecurrent of
295v 1110 = 00026576577 amperes = 266 ma
RTL is a relatively old technology and the transistors used in RTL ICs have a dc forwardcurrent gain of around 30 If we assume a current gain of 30 266 ma base current will
support a maximum of 798 ma collector current However if we drop all but 03 volts acrossthe 640 collector resistor it will carry 33640 = 51 ma Therefore this transistor is indeedfully saturated it is turned on as hard as it can be
With a logic 1 input then this circuit produces a logic 0 output We have already seen thata logic 0 input will produce a logic 1 output Hence this is a basic inverter circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 731
As we can see from the above calculations the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation Therefore wehave the possibility of using one output to drive multiple inputs of other gates and of havinggates with multiple input resistors Such a circuit is shown to the right
In this circuit we have four input resistors Raising any one input to +36 volts will besufficient to turn the transistor on and applying additional logic 1 (+36 volt) inputs will notreally have any appreciable effect on the output voltage Remember that the forward biasvoltage on the transistors base will not exceed 065 volt so the current through a groundedinput resistor will not exceed 065v470 = 1383 ma This does provide us with a practicallimit on the number of allowable input resistors to a single transistor but doesnt cause anyserious problems within that limit
The RTL gate shown above will work but has a problem due to possible signalinteractions through the multiple input resistors A better way to implement the NOR functionis shown to the left
Here each transistor has only one input resistor so there is no interaction between inputsThe NOR function is performed at the common collector connection of all transistors whichshare a single collector load resistor
This is in fact the pattern for all standard RTL ICs The very commonly-used microL914 is adual two-input NOR gate where each gate is a two-transistor version of the circuit to the leftIt is rated to draw 12 ma of current from the 36V power supply when both outputs are at
logic 0 This corresponds quite well with the calculations we have already made
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 831
Standard fan-out for RTL gates is rated at 16 However the fan-in for a standard RTL gateinput is 3 Thus a gate can produce 16 units of drive current from the output but requires 3units to drive an input There are low-power versions of these gates that increase the values of the base and collector resistors to 15K and 36K respectively Such gates demand lesscurrent and typically have a fan-in of 1 and a fan-out of 2 or 3 They also have reduced
frequency response so they cannot operate as rapidly as the standard gates To get greater output drive capabilities buffers are used These are typically inverters which have beendesigned with a fan-out of 80 They also have a fan-in requirement of 6 since they use pairsof input transistors to get increased drive
We can get a NAND function in either of two ways We can simply invert the inputs to the NOROR gate thus turning it into an ANDNAND gate or we can use the circuit shown tothe right
In this circuit each transistor has its own separate input resistor so each is controlled by adifferent input signal However the only way the output can be pulled down to logic 0 is if
both transistors are turned on by logic 1 inputs If either input is a logic 0 that transistor cannot conduct so there is no current through either one The output is then a logic 1 This isthe behavior of a NAND gate Of course an inverter can also be included to provide an ANDoutput at the same time
The problem with this NAND circuit stems from the fact that transistors are not idealdevices Remember that 03 volt collector saturation voltage Ideally it should be zero Sinceit isnt we need to look at what happens when we stack transistors this way With two the
combined collector saturation voltage is 06 volt -- only slightly less than the 065 volt basevoltage that will turn a transistor on
If we stack three transistors for a 3-input NAND gate the combined collector saturationvoltage is 09 volt This is too high it will promote conduction in the next transistor no matter what In addition the load presented by the upper transistor to the gate that drives it will bedifferent from the load presented by the lower transistor This kind of unevenness can causesome odd problems to appear especially as the frequency of operation increases Because of these problems this approach is not used in standard RTL ICs
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 931
Diode-Transistor Logic
As we said in the page on diode logic the basic problem with DL gates is that they rapidly
deteriorate the logical signal However they do work for one stage at a time if the signal is re-amplified between gates Diode-Transistor Logic (DTL) accomplishes that goal
The gate to the right is a DL OR gate followed by an inverter such as the one we looked at in the page on resistor-transistor logic The OR function is still performed by the diodes Howeverregardless of the number of logic 1 inputs there is certain to be a high enough input voltage to drivethe transistor into saturation Only if all inputs are logic 0 will the transistor be held off Thus this
circuit performs a NOR function
The advantage of this circuit over its RTL equivalent is that the OR logic is performed by thediodes not by resistors Therefore there is no interaction between different inputs and any number of diodes may be used A disadvantage of this circuit is the input resistor to the transistor Its
presence tends to slow the circuit down thus limiting the speed at which the transistor is able toswitch states
At first glance the NAND version shown on the left should eliminate this problem Any logic 0input will immediately pull the transistor base down and turn the transistor off right
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1031
Well not quite Remember that 065 volt base input voltage for the transistor Diodes exhibit a verysimilar forward voltage when theyre conducting current Therefore even with all inputs at groundthe transistors base will be at about 065 volt and the transistor can conduct
To solve this problem we can add a diode in series with the transistors base lead as shown to theright Now the forward voltage needed to turn the transistor on is 13 volts For even moreinsurance we could add a second series diode and require 195 volts to turn the transistor on Thatway we can also be sure that temperature changes wont significantly affect the operation of thecircuitEither way this circuit will work as a NAND gate In addition as with the NOR gate we canuse as many input diodes as we may wish without raising the voltage threshold Furthermore withno series resistor in the input circuit there is less of a slowdown effect so the gate can switch statesmore rapidly and handle higher frequencies The next obvious question is can we rearrange thingsso the NOR gate can avoid that resistor and therefore switch faster as well
The answer is Yes there is Consider the circuit shown to the left Here we use separate transistorsconnected together Each has a single input and therefore functions as an inverter by itselfHowever with the transistor collectors connected together a logic 1 applied to either input willforce the output to logic 0 This is the NOR function
We can use multiple input diodes on either or both transistors as with the DTL NAND gate Thiswould give us an AND-NOR function and is useful in some circumstances Such a construction isalso known as an AOI (for AND-OR-INVERT) circuit
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1131
Transistor-Transistor Logic
Transistor-Transistor Logic
With the rapid development of integrated circuits (ICs) new problems were encountered and newsolutions were developed One of the problems with DTL circuits was that it takes as much room onthe IC chip to construct a diode as it does to construct a transistor Since real estate is exceedinglyimportant in ICs it was desirable to find a way to avoid requiring large numbers of input diodesBut what could be used to replace many diodes
Well looking at the DTL NAND gate to the right we might note that the opposed diodes look pretty much like the two junctions of a transistor In fact if we were to have an inverter it wouldhave a single input diode and we just might be able to replace the two opposed diodes with an NPNtransistor to do the same job
In fact this works quite nicely The figure to the left shows the resulting inverter
In addition we can add multiple emitters to the input transistor without greatly increasing theamount of space needed on the chip This allows us to construct a multiple-input gate in almost thesame space as an inverter The resulting savings in real estate translates to a significant savings inmanufacturing costs which in turn reduces the cost to the end user of the device
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1231
One problem shared by all logic gates with a single output transistor and a pull-up collector resistor is switching speed The transistor actively pulls the output down to logic 0 but the resistor is notactive in pulling the output up to logic 1 Due to inevitable factors such as circuit capacitances and acharacteristic of bipolar transistors called charge storage it will take a certain amount of time for the transistor to turn completely off and the output to rise to a logic 1 level This limits thefrequency at which the gate can operate
The designers of commercial TTL IC gates reduced that problem by modifying the output circuitThe result was the totem pole output circuit used in most of the 74005400 series TTL ICs Thefinal circuit used in most standard commercial TTL ICs is shown to the right The number of inputsmay vary mdash a commercial IC package might have six inverters four 2-input gates three 3-inputgates or two 4-input gates An 8-input gate in one package is also available But in each case thecircuit structure remains the same
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1331
Emmiter-Coupled Logic
Emitter-Coupled Logic is based on the use of a multi-input differential amplifier to amplify andcombine the digital signals and emitter followers to adjust the dc voltage levels As a result noneof the transistors in the gate ever enter saturation nor do they ever get turned completely off Thetransistors remain entirely within their active operating regions at all times As a result thetransistors do not have a charge storage time to contend with and can change states much morerapidly Thus the main advantage of this type of logic gate is extremely high speed
The schematic diagram shown here is taken from Motorolas 100010000 series of MECL devicesThis particular circuit is of one 4-input ORNOR gate Standard voltages for this circuit are -52volts (VEE) and ground (VCC) Unused inputs are connected to VEE The bias circuit at the right sideconsisting of one transistor and its associated diodes and resistors can handle any number of gates
in a single IC package Typical ICs include dual 4-input triple 3-input and quad 2-input gates Ineach case the gates themselves differ only in how many input transistors they have A single biascircuit serves all gates
In operation a logical ouput changes state by only 085 volt from a low of -160 volts to a high of -075 volt The internal bias circuit supplies a fixed voltage of -1175 volts to the bias transistor inthe differential amplifier If all inputs are at -16 volts (or tied to VEE) the input transistors will all
be off and only the internal differential transistor will conduct current This reduces the basevoltage of the OR output transistor lowering its output voltage to -160 volts At the same time noinput transistors are affecting the NOR output transistors base so its output rises to -075 volt Thisis simply the emitter-base voltage VBE of the transistor itself (All transistors are alike within the
IC and are designed to have a VBE of 075 volt)
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1431
When any input rises to -075 volt that transistor siphons emitter current away from the internaldifferential transistor causing the outputs to switch states
The voltage changes in this type of circuit are small and are dictated by the VBE of the transistorsinvolved when they are on Of greater importance to the operation of the circuit is the amount of
current flowing through various transistors rather than the precise voltages involved AccordinglyEmitter-Coupled Logic is also known as Current Mode Logic (CML) This is not the onlytechnology to implement CML by any means but it does fall into that general description In anycase this leads us to a major drawback of this type of gate it draws a great deal of current from the
power supply and hence tends to dissipate a significant amount of heat
To minimize this problem some devices such as frequency counters use an ECL decade counter atthe input end of the circuitry followed by TTL or high-speed CMOS counters at the later digit
positions This puts the fast expensive IC where it is absolutely required and allows us to usecheaper ICs in locations where the signal will never be at that high a frequency
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1531
Diode Logic
Diode Logic makes use of the fact that the electronic device known as a diode will conduct an
electrical current in one direction but not in the other In this manner the diode acts as an electronicswitch
To the left you see a basic Diode Logic OR gate Well assume that a logic 1 is represented by +5volts and a logic 0 is represented by ground or zero volts In this figure if both inputs are leftunconnected or are both at logic 0 output Z will also be held at zero volts by the resistor and willthus be a logic 0 as well However if either input is raised to +5 volts its diode will becomeforward biased and will therefore conduct This in turn will force the output up to logic 1 If bothinputs are logic 1 the output will still be logic 1 Hence this gate correctly performs a logical OR function
To the right is the equivalent AND gate We use the same logic levels but the diodes are reversed
and the resistor is set to pull the output voltage up to a logic 1 state For this example +V = +5volts although other voltages can just as easily be used Now if both inputs are unconnected or if they are both at logic 1 output Z will be at logic 1 If either input is grounded (logic 0) that diodewill conduct and will pull the output down to logic 0 as well Both inputs must be logic 1 in order for the output to be logic 1 so this circuit performs the logical AND function
In both of these gates we have made the assumption that the diodes do not introduce any errors or losses into the circuit This is not really the case a silicon diode will experience a forward voltagedrop of about 065v to 07v while conducting But we can get around this very nicely by specifyingthat any voltage above +35 volts shall be logic 1 and any voltage below +15 volts shall be logic 0It is illegal in this system for an output voltage to be between +15 and +35 volts this is the
undefined voltage region
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1631
Individual gates like the two above can be used to advantage in specific circumstances Howeverwhen DL gates are cascaded as shown to the left some additional problems occur Here we havetwo AND gates whose outputs are connected to the inputs of an OR gate Very simple andapparently reasonable
But wait a minute If we pull the inputs down to logic 0 sure enough the output will be held at logic0 However if both inputs of either AND gate are at +5 volts what will the output voltage be Thatdiode in the OR gate will immediately be forward biased and current will flow through the ANDgate resistor through the diode and through the OR gate resistor
If we assume that all resistors are of equal value (typically they are) they will act as a voltagedivider and equally share the +5 volt supply voltage The OR gate diode will insert its small lossinto the system and the output voltage will be about 21 to 22 volts If both AND gates have logic1 inputs the output voltage can rise to about 28 to 29 volts Clearly this is in the forbidden zonewhich is not supposed to be permitted
If we go one step further and connect the outputs of two or more of these structures to another ANDgate we will have lost all control over the output voltage there will always be a reverse-biaseddiode somewhere blocking the input signals and preventing the circuit from operating correctlyThis is why Diode Logic is used only for single gates and only in specific circumstances
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1731
Referecircncias Bibliograacuteficas
DIGITAL ELECTRONIC Diode Logic Disponiacutevel em httpwwwplay-hookeycomdigitalelectronicsdl_gateshtml Acessado em 28 Jul2010
______________________ Diode Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsdtl_gateshtml Acessado em 28 Jul2010
______________________ Emitter-Coupled Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsecl_gateshtml Acessado em 28 Jul2010
______________________ Resistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsrtl_gateshtml Acessado em 28 Jul2010
______________________ Transistor Transistor Logic Disponiacutevel em httpwwwplay-
hookeycomdigitalelectronicsttl_gateshtml Acessado em 28 Jul2010
ETB ndash Escola Teacutecnica de Brasiacutelia Teacutecnicas de Leitura Disponiacutevel em
httpziggiuolcombrsitedwnld3592 Acessado em 21 jul 2010
HEF4081B ndash Quadruple 2 ndash Input and gate Disiponiacutevel em
wwwnxpcomdocumentsdata_sheetHEF4081Bpdf Acessado em 28 jul 2010
HEF4511B ndash BDC to 7 ndash Segment Latchdecoderdriver Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4511Bpdf Acessado em 28 Jul 2010
HEF4017B ndash Stage Jonhson Counter Disponiacutevel em
httpwwwnxpcomdocumentsdata_sheetHEF4017Bpdf Acessado em 28 Jul 2010
HEF4029B ndash Synchronous updown counter binary decade Counter Disponiacutevel
em httpicsnxpcomproductshefdatasheethef4029bpdf Acessado em 28 Jul 2010
HEF 4049 ndash Hex Inverting Buffers Disponiacutevel em
httpicsnxpcomproductshefdatasheethef4049bpdf Acessado em 28 Jul 2010
PHILIPS ndash Integrated Circuits ndash HE 4000B- Logic Family CMOS In Philips
Eletronics North America Corporation Printed in USA 1996p 211 267 343 429
485
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1831
RESISTORS Disponiacutevel em
httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010
SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em
httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 1931
Lista de textos
The Microprocessor
The term microprocessor typically refers to the central processing unit (CPU) of a microcomputer containing the arithmetic logic unit (ALU) and the control units It is typically implemented on a single LSI chip This separates the brains of theoperation from the other units of the computer
An example of
microprocessor
architecture
The microprocessor contains the arithmetic logicunit (ALU) and the control unitfor a microcomputer It isconnected to memory and IO
by buses which carry
information between the units
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2031
Microcomputer
Example
Typical microcomputersemploy a microprocessor unit(MPU) a clock andinterfaces to memory andexternal inputoutput devicesThe units are connected by
buses which transfer information between them
Buses The exchange of information
Information is transferred between units of the microcomputer by collections of conductors called buses
There will be one conductor for each bit of information to be passed eg 16lines for a 16 bit address bus There will be address control and data buses
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2131
Arithmetic Logic Unit
All the arithmetic operations of a microprocessor take place in the arithmeticlogic unit (ALU) Using a combination of gates and flip-flops numbers can be
added in less than a microsecond even in small personal computers The operationto be performed is specified by signals from the control unit The data upon whichoperations are performed can come from memory or an external input The datamay be combined in some way with the contents of the accumulator and the resultsare typically placed in the accumulator From there they may be transferred tomemory or to an output unit
The Accumulator
The accumulator is the principal register of the arithmetic logic unit of amicroprocessor Registers are sets of flip-flops which can hold data Theaccumulator typically holds the first piece of data for a calculation If a number from memory is added to that date the sum replaces the original data in theaccumulator It is the repository for successive results of arithmetic operationswhich may then be transferred to memory to an output device etc
Control Unit of Microprocessor
The control unit of a microprocessor directs the operation of the other units by providing timing and control signals It is the function of the microcomputer toexecute programs which are stored in memory in the form of instructions and dataThe control unit contains the necessary logic to interpret instructions and togenerate the signals necessary for the execution of those instructions Thedescriptive words fetch and execute are used to describe the actions of thecontrol unit It fetches an instruction by sending and address and a read commandto the memory unit The instruction at that memory address is transferred to thecontrol unit for decoding It then generates the necessary signals to execute the
instruction
httphyperphysicsphy-astrgsueduhbaseelectronicmicroprohtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2231
Number Systems
Digital circuits are inherently binary in nature but several types of representations of numerical data are in use
The representation of an unsigned integer can be done in binary octal decimalor hexadecimal For display purposes each decimal digit is often represented by afour-bit binary number in a system called binary coded decimal (BCD)Conversions between these representations can be handled in a routine manner
The representation of signed numbers presents more problems and those problems are addressed in various ways Some of the codes used are signmagnitude offset binary 2s complement excess-3 4221 and Gray Atable can show the display of four-bit integers
Alphanumeric CodingFor the inherently binary world of the computer it is necessary to put all
symbols letters numbers etc into binary form The most commonly usedalphanumeric code is the ASCII code with others like the EBCDIC code beingapplied in some communication applications
ASC
IICod
e
EBCDI
C
Code
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2331
Parity Checks
Errors in digital code will result in the changing of a 0 to a 1 or vice versa One helpfulmethod for determining if a single error of that type has ocurred is to check theevenness or oddness of the sum of the set bits To facilitate this check an extra bit calledthe parity bit is added to each word in a data transmission In the even-parity method the
parity bit is chosen so that the total number of 1s including the parity bit is even Thereceiver checks the parity to detect any single-bit errors The same thing can beaccomplished with an odd-parity method so it is necessary to know which is being used
in order to communicate with a host computer It will also be necessary to know howmany data bits and how many stop bits are being used
Serial Communication Protocols
Serial communication protocols for data include the RS-232 protocol whichhas been used for communication of modems The MIDI protocol for music andsound applications is also a serial protocol
Note This is just a place-holder location for future development Very little has been done with it to date
RS-232 Serial Communication Protocol
The most common standard used for serial data transmission is called RS232C It wasset by the Electronics Industry Association and includes an assignment of theconductors in a 25-pin connector It has also been used widely for data transfer over amodem
ModemFor serial digital data transmission over telephone lines the logic levels are
converted to audio tones at one end (modulation) and then back into logic levels atthe other end (demodulation) The device which accomplishes this is called amodem for modulator-demodulator The acoustic modem converts logic 1 to a2225 Hz sine wave burst and a logic zero into a 2025 Hz tone As a receiver ittreats 1270 Hz as a logic 1 and 1070 Hz as a logic 0 This technique calledfrequency-shift keying allows the same phone line to be used simultaneously for sending and receiving in what is called full-duplex operation The modem at the
other end of the line must receive 2225 Hz as a logic 1 and send 1270 Hz as a logic
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2431
1 A basic rate of transmission is 300 baud but data lines up to 56K baud are inuse
MIDI Communication Protocol
Musical Instrument Digital Interface (MIDI) is a serial data transfer protocol Ituses one start bit eight data bits and two stop bits and operates at 3125 kilobaudIt uses two lines for input devices and three lines for output devices Thecontrolling device and the instrument controlled are electrically isolated from oneanother by the use of an opto-isolator and the avoidance of direct commongrounds The controlling device sends a signal through a UART to a 5-pinDINMIDI out connector On the input side the signal drives the LED of anoptoisolator and the output of the optoisolator is sent to the UART of the receivingdevice for conversion to parallel information
In controlling a device in an integrated music system the status byte describesthe action to be taken while the data bytes provide specific values or other instructions for the type of action requested
UART
The conversion of parallel data inside a computer to serial data for use in serialcommunication is accomplished by a Universal AsynchronousReceiverTransmitter (UART) UART chips are used for RS-232 and MIDI communication
Parallel Communication Protocols
Parallel communication protocols for data include the IEEE-488 protocol andthe Centronics protocol has been widely used for printers
Note This is just a place-holder location for future development Very little has been done with it to date
IEEE-488 ParallelHewlett-Packard developed a communication bus which has become the industrystandard for laboratory use It is also known as the GPIB (General PurposeInstrumentation Bus) or the HPIB (Hewlett-Packard Instrumentation Bus) It is a 24 line
bus with the following allocation of lines 16 bi-directional lines (8 data lines and 8control lines) and 8 additional lines for logical ground returns and shielding It canconnect up to 14 instruments with a computer and operate at a data rate as high as 1 MB
per second
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2531
Most manufacturers of research equipment which communicates with a computer offer IEEE-488 devices Such devices can be classified as 1) listen only 2) talk only 3) talk-listen and 4) talk-listen-control
Analog-to-Digital Conversion
This is a sample of the large number of analog-to-digital conversion methodsThe basic principle of operation is to use the comparator principle to determinewhether or not to turn on a particular bit of the binary number output It is typicalfor an ADC to use a digital-to-analog converter (DAC) to determine one of theinputs to the comparator
Digital Ramp ADC
Conversion from analog to digital form inherently involves comparator actionwhere the value of the analog voltage at some point in time is compared with somestandard A common way to do that is to apply the analog voltage to one terminalof a comparator and trigger a binary counter which drives a DAC The output of the DAC is applied to the other terminal of the comparator Since the output of theDAC is increasing with the counter it will trigger the comparator at some pointwhen its voltage exceeds the analog input The transition of the comparator stopsthe binary counter which at that point holds the digital value corresponding to theanalog voltage
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2631
Successive Approximation ADCIllustration of 4-bit SAC with 1 volt step size (after Tocci Digital Systems)
The successiveapproximation ADC is muchfaster than the digital rampADC because it uses digitallogic to converge on the valueclosest to the input voltage Acomparator and a DAC are usedin the process
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2731
Flash ADC
Illustrated is a 3-bit flash ADC with resolution
1 volt (after Tocci) The resistor net and
comparators provide an input to the
combinational logic circuit so the conversiontime is just the propagation delay through
the network - it is not limited by the clock
rate or some convergence sequence It is
the fastest type of ADC available but
requires a comparator for each value of
output (63 for 6-bit 255 for 8-bit etc) Such
ADCs are available in IC form up to 8-bit and
10-bit flash ADCs (1023 comparators) are
planned The encoder logic executes a truth
table to convert the ladder of inputs to thebinary number output
Comparator
The extremely large open-loop
gain of an op-amp makes it anextremely sensitive device for comparing its input with zero For
practival purposes if
the output is driven to the positive supply voltage and if
it is driven to the negativesupply voltage The switchingtime for - to + is limited by theslew rate of the op-amp
Comparator Applications
The basic comparator will swing its output to at the slightest difference
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2831
between its inputs But there are many variations where the output is
designed to switch between two other voltage values Also the input may be
tailored to make a comparison to an input voltage other than zero
httphyperphysicsphy-astrgsueduhbaseelectronicopampvar8htmlc2
Digital-to-Analog Conversion
When data is in binary form the 0s and 1s may be of several forms such as theTTL form where the logic zero may be a value up to 08 volts and the 1 may be avoltage from 2 to 5 volts The data can be converted to clean digital form usinggates which are designed to be on or off depending on the value of the incomingsignal Data in clean binary digital form can be converted to an analog form byusing a summing amplifier For example a simple 4-bit DA converter can bemade with a four-input summing amplifier More practical is the R-2R Network
DAC
Four-Bit DA Converter
One way to achieve DA conversion is to use a summing amplifier
This approach is not satisfactory for a large number of bits because it requires too
much precision in the summing resistors This problem is overcome in the R-2R
network DAC
R-2R Ladder DAC
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 2931
The summing amplifier with the R-2R ladder of resistances shown produces theoutput
where the Ds take the value 0 or 1 Thedigital inputs could be TTL voltages whichclose the switches on a logical 1 and leaveit grounded for a logical 0 This isillustrated for 4 bits but can be extended toany number with just the resistance valuesR and 2R
R-2R Ladder DAC Details
httphyperphysicsphy-astrgsueduhbaseelectronicdachtmlc4
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3031
The 555 Timer
Following Forrest Mims in laying out the 555 Timer IC as a block diagramallows one to focus on the functions of the circuit
Very popular for its versatility the 555 Timer IC can operate in either astable or monostable multivibrator mode resulting in a variety of applications
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
862019 Ingles Instrumental Eletroeletronica2
httpslidepdfcomreaderfullingles-instrumental-eletroeletronica2 3131
This IC contains 23 transistors 2diodes and 16 resistors
Supply voltage 45 to
15
Supply current 3 to 6
mA 5V
10 to 15mA15V
Output current200mA max
Power dissipation
600mW
8-pin mini DIP
556 is 14 pin dual
555
One-Chip RegulatorsMany if not most small power supplies today are built with the aid of a family
of one-chip regulators which use zener diodes and several transistors to regulatethe output of a rectifier These remarkable devices provide stable ripple-freeoutput DC voltages under a wide range of operating conditions
An example is Fairchilds micro A7800 series of 3-terminal positive voltageregulators In a single monolithic package they incorporate two zener diodes 17transistors 21 resistors and a capacitor according to the manufacturers equivalentcircuit They incorporate internal current limiting and thermal shutdown features
and can produce on the order of an ampere of output current
httphyperphysicsphy-astrgsueduhbaseelectronicchipreghtmlc1
top related