Ingles Instrumental Eletroeletronica2

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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



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



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



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



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

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Diamet

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(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

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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



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



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



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



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



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



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



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)



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



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



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



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


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



RESISTORS Disponiacutevel em

httphyperphysicsphytrgsueduhbaseelectricresishtmlc1 Acessado em 26 jul 2010

SEMICONDUTORES A verdadeira Histoacuteria do Transistor Disponiacutevel em

httpwwwbncombrradios-antigossemicondhtm Acessado em 28 Jul 2010



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



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



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



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



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



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


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



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



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



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



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



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



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



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



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




















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485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

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EBCDI

C

Code



Parity Checks


















UART







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Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555

























and area A = cm2







gauges

for copper wire

AW

G

Diamet

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Typical use


12 00808Household

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Copper172

4Silver 159

Iron 971

Platinu

m 106

Nichrom

e100

Tungst

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thornyuml thornyuml

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295v 1110 = 00026576577 amperes = 266 ma





































































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

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EBCDI

C

Code



Parity Checks


















UART







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Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555

















and area A = cm2







gauges

for copper wire

AW

G

Diamet

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(inches)

Typical use


12 00808Household

circuit




Aluminu

m265 Gold 224

Copper172

4Silver 159

Iron 971

Platinu

m 106

Nichrom

e100

Tungst

en565



thornyuml thornyuml

thornyuml

thornyuml

thornyuml

thornyuml thornyuml

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295v 1110 = 00026576577 amperes = 266 ma





































































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555









and area A = cm2







gauges

for copper wire

AW

G

Diamet

er

(inches)

Typical use


12 00808Household

circuit




Aluminu

m265 Gold 224

Copper172

4Silver 159

Iron 971

Platinu

m 106

Nichrom

e100

Tungst

en565



thornyuml thornyuml

thornyuml

thornyuml

thornyuml

thornyuml thornyuml

thornyuml








295v 1110 = 00026576577 amperes = 266 ma





































































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555













295v 1110 = 00026576577 amperes = 266 ma





































































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555







































































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







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Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









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mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555































































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555





















































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555











































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555





































Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555





























Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

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EBCDI

C

Code



Parity Checks


















UART







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Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555

























Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







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Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555
















Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








Diode Logic








































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555






































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555
































485









Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555














Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








Lista de textos

The Microprocessor


An example of

microprocessor

architecture






Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








Microcomputer

Example











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555











The Accumulator




instruction




Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








Number Systems






ASC

IICod

e

EBCDI

C

Code



Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








Parity Checks


















UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555












UART







per second






Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555











Digital Ramp ADC








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555












Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








Flash ADC














Comparator
















DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555














DAC





network DAC

R-2R Ladder DAC









The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555














The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555








The 555 Timer







15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555










15


mA 5V

10 to 15mA15V


Power dissipation

600mW

8-pin mini DIP

556 is 14 pin dual

555






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