Fundamentals of Electronics - Awais Yasin

7/30/2019 Fundamentals of Electronics - Awais Yasin

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FUNDAMENTALS OF ELECTRONICS

COMPILED BY:

AWAIS YASIN

(COURSE MATERIAL FOR DEPARTMENTAL PROMOTION EXAMINATION (DPE))


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2FUNDAMENTALS OF ELECTRONICS

TABLE OF CONTENTS

CHAPTER 1: REVIEW OF BASIC CONCEPTS ............................................................................. 8BASIC UNDERSTANDING ..................................................................................................... 8

BALANCEOFCHARGE........................................................................................................ 8

CONDUCTORS ....................................................................................................................... 9

INSULATORS.......................................................................................................................... 9

QUANTITYOFCHARGE..................................................................................................... 10

FORCEBETWEENCHARGES:COULOMB'SLAW...................................................... 10

VOLTAGE,CURRENT,ANDPOWERRELATEDCONCEPTS.................................... 12

RESISTORS .......................................................................................................................... 19

Load ........................................................................................................ 20

Labeling ................................................................................................... 21

Color System ............................................................................................ 22

Construction ............................................................................................. 22

Resistively of the Material .......................................................................... 22

Resistor Junctions ..................................................................................... 25

Resistor variations ..................................................................................... 26

Applications .............................................................................................. 27

Specifications ........................................................................................... 28

CAPACITORS ....................................................................................................................... 31

Capacitance .............................................................................................. 32

Capacitor Labeling ..................................................................................... 33

Construction ............................................................................................. 35

Capacitor Materials .................................................................................... 35

Capacitor Junctions ................................................................................... 36

Capacitors in Series ................................................................................... 36

Capacitors in Parallel ................................................................................. 36

RC CIRCUITS ......................................................................................................................... 37

TheTimeConstant .................................................................................................................. 38

GeneralNotesaboutCapacitors ........................................................................................... 40

INDUCTORS ........................................................................................................................... 40

Introduction ............................................................................................. 40

Important Qualities of Inductors ................................................................. 41

Inductance ............................................................................................... 43

Quality factor: Q ....................................................................................... 44Impedance ............................................................................................... 45


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Inductive Networks ................................................................................... 45

OTHER COMPONENTS ........................................................................................................ 48

Ideal voltage sources ................................................................................. 48

Ideal current sources ................................................................................. 48

Switch ..................................................................................................... 48

Contact Arrangements ............................................................................... 49

DC VOLTAGE AND CURRENT LAWS............................................................................... 51

Ohm's Law ............................................................................................... 51

Kirchhoffs Current Law .............................................................................. 53

Consequences of KVL and KCL .................................................................... 53

NODAL ANALYSIS ............................................................................................................... 57

MESH ANALYSIS .................................................................................................................. 60

THEVENIN / NORTON EQUIVALENTS ............................................................................. 62

Thevenins Equivalents............................................................................... 62

Norton Equivalents .................................................................................... 63

SUPERPOSITION ................................................................................................................... 66

DIAGNOSTIC EQUIPMENT ................................................................................................. 69

DC CIRCUIT ANALYSIS ...................................................................................................... 71

CHAPTER 2: AC CIRCUITS ........................................................................................................... 76

RELATIONSHIP BETWEEN VOLTAGE AND CURRENT ................................................ 76

PHASORS ............................................................................................................................... 77

IMPEDANCE .......................................................................................................................... 78

STEADY STATE .................................................................................................................... 80

CHAPTER 3: TRANSIENT ANALYSIS ......................................................................................... 81

RC CIRCUITS ............................................................................................ 81

RLC CIRCUITS .......................................................................................... 82

CHAPTER 4: ANALOG CIRCUITS ................................................................................................ 87

PASSIVE VERSUS ACTIVE COMPONENTS .................................................................. 88

VACUUM TUBES .................................................................................................................. 88

DIODES ................................................................................................................................... 92

TRANSISTORS ....................................................................................................................... 95

AMPLIFIERS ........................................................................................................................ 104

TRANSISTOR AMPLIFIER CONFIGURATIONS ............................................................. 105

CLASSES ............................................................................................... 108

OPERATIONAL AMPLIFIER ............................................................................................. 109

IDEALOPAMPS...................................................................................................... 113

BASICOP-AMPCONFIGURATIONS................................................................... 114INVERTINGOPAMP.......................................................................... 114


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NON-INVERTINGOPAMP .................................................................. 117

ADVANCEDOP-AMPCONFIGURATIONS ........................................................ 119

Voltage Follower ................................................................................................................... 119

Difference amplifier ................................................................ ............................................... 120

Summing amplifier ................................................................................................................ 121

Integrator ............................................................. ................................................................. .. 122

Differentiator ................................................................. ......................................................... 123

Real Op Amps ............................................................... ......................................................... 123

DC Behaviour ........................................................................................................................ 124

AC Behaviour ........................................................................................................................ 124

Applications .................................................................. ......................................................... 124

Other Notation ....................................................................................................................... 125

Oscillators .............................................................................................................................. 125

ANALOG MULTIPLIERS ................................................................ .................................... 125

Diode Implementations ............................................................ .............................................. 126

MOS implementation ............................................................... .............................................. 128

CHAPTER 5:DIGITAL CIRCUITS130

OVERVIEW ............................................................................................. 130

BOOLEAN ALGEBRA ................................................................................. 130

Formal Mathematical Operators ............................................................................................... 131

Boolean algebra Laws .............................................................................................................. 132

Associatively ................................................................... ......................................................... 132

Distributives ............................................................................................................................. 132

Commutatively ................................................................ ......................................................... 132

De Morgan's Law ................................................................................................................... .. 132

Notes......................................................................................................................................... 133

Rules .......................................................... ................................................................. .............. 133

Examples .................................................................................................................................. 134

TTL ........................................................................................................ 134

The NOT Gate ............................................................... ......................................................... 134

TTL Inverter (NOT Gate) ...................................................................................................... 135

CMOS .................................................................................................................................... 135

Logic Gates ............................................................................................................................ 136

NOT ....................................................................................................................................... 136

NAND ................................................................ ................................................................ .... 136

AND .................................................................. ................................................................... .. 137

NOR .................................................................. ................................................................... .. 137

OR ........................................................... ................................................................. .............. 137XNOR .................................................................................................................................... 138


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XOR .................................................................. ................................................................... .. 138

INTEGRATED CIRCUIT ..................................................................................................... 138

Overview ............................................................. ................................................................. .. 139

ELEMENTS OF DIGITAL CIRCUITS ............................................................. 139

TRANSISTOR .............................................................. ......................................................... 139

Field Effect Transistor ........................................................................................................... 140

Complementary Metal Oxide Semiconductor .......................................................... .............. 140

Bipolar Junction Transistor .................................................................................................... 141

Construction .................................................................. ......................................................... 141

NPN ....................................................................................................................................... 141

PNP ........................................................................................................................................ 141

Operation................................................................................................................................ 141

BASIC GATES ............................................................. ......................................................... 141

Overview ............................................................. ................................................................. .. 141

Explanation of the gates' operation ........................................................................................ 142

LATCHES AND FLIP FLOPS ............................................................ .................................. 145

RS Flip Flops ......................................................................................................................... 145

D Flip Flops ........................................................................................................................... 146

Toggle Flip Flops .......................................................... ......................................................... 146

JK Flip Flops ................................................................. ......................................................... 147

COUNTERS .......................................................................................................................... 147

Ripple Counters ..................................................................................................................... 147

Synchronous Counters ........................................................................................................... 147

ADDERS................................................................................................................................ 148

Half Adders ................................................................... ......................................................... 148

Full Adders............................................................................................................................. 149

MULTIPLEXERS ......................................................... ......................................................... 150

Overview ............................................................. ................................................................. .. 150

Multiplexer Based Logic .......................................................... .............................................. 150

DECODERS AND ENCODERS ........................................................................................... 151

Decoders ................................................................................................................................ 151

Encoders .............................................................. ................................................................. .. 151

CHAPTER 6: MICROPROCESSORS ........................................................................................... 152

Types of Processors ............................................................................................................... 152

Types of Use .......................................................................................................................... 154

Abstraction Layers ................................................................. ................................................ 154

Moore's Law .......................................................................................................................... 155

Basic Elements of a Computer ............................................................. .................................. 157

Computer Architecture ............................................................. .............................................. 157


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Control ................................................................................................................................... 158

Datapath .............................................................. ................................................................. .. 158

Microprocessor Components ................................................................................................. 159

Instruction Set Architectures ................................................................ .................................. 161

Common Instructions ............................................................... .............................................. 162

Memory ............................................................... ................................................................. .. 162

Microprocessor Components ................................................................................................. 168

Basic Components.................................................................................................................. 168

Registers .............................................................. ................................................................. .. 168

Register File .................................................................. ......................................................... 168

Multiplexers .................................................................. ......................................................... 168

Program Counter ........................................................... ......................................................... 169

Instruction Decoder ................................................................ ................................................ 169

The Instruction Decoder reads the next instruction in from memory, and sends the component

peices of that instruction to the necessary destinations ........................................................ .. 169

RISC Instruction Decoder ...................................................................................................... 169

CISC Instruction Decoder ...................................................................................................... 169

Register File .................................................................. ......................................................... 170

Register File .................................................................. ......................................................... 170

Register Bank ................................................................ ......................................................... 171

Memory Unit ................................................................. ......................................................... 172

Memory Unit ................................................................. ......................................................... 172

Actions of the Memory Unit .................................................................................................. 172

Timing Issues ................................................................ ......................................................... 172

ALU ....................................................................................................................................... 172

Tasks of an ALU .................................................................................................................. .. 173

ALU Slice .............................................................................................................................. 173

Additional Operations .............................................................. .............................................. 175

ALU Configurations .............................................................................................................. 175

Accumulator .................................................................. ......................................................... 176Register-to-Register ................................................................ ............................................... 177

Register Stack ........................................................................................................................ 178

Register-and-Memory .............................................................. .............................................. 179

Complicated Structures ............................................................ .............................................. 179

Example: IA-32 ............................................................. ......................................................... 179

Example: MIPS ............................................................. ......................................................... 180

Floating Point Unit (FPU) ........................................................ .............................................. 180

Floating point numbers .......................................................................................................... 180

IEEE 754 ............................................................. ................................................................. .. 180


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Floating Point Multiplication ................................................................................................. 181

Floating Point Addition ............................................................ .............................................. 181

Floating Point Unit Design .................................................................................................... 181

Control Unit ........................................................................................................................... 182

Simple Control Unit ............................................................................................................... 182

Complex Control Unit .............................................................. .............................................. 182

References: ............................................................................................................................. 182

Suggested Reading Material for further reading .................................................................... 183

Sample Paper (MCQs): .......................................................................................................... 183


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CHAPTER 1: REVIEW OF BASIC CONCEPTS

BASIC UNDERSTANDING

Materialsthatallowelectronstoflowwithminimalresistance.

Materialsthatpreventtheflowofelectrons.

Materialswhosebehaviorrangesbetweenthatofaconductorandthatof

an insulatorunder differentconditions.Their conductingbehavior ismainly dependent on

temperature.

Anatomcontainsanucleusandoneormoreelectrons.Theatomexistsinthree

states: neutral,positively charged,and negatively charged.Aneutralatomhas the same

numberofelectronsandprotons,apositivelychargedatomhasmoreprotonsthanelectrons

andanegativelychargedatomhasmoreelectronsthanprotons.

(+)and(-)Ions

Anionisanatomthathasanunequalnumberofelectronsandprotons.Thenatureofatoms

istotrytohaveanequalamountofprotonsandelectrons.Thepositivesideofthebattery

has + ions, meaning there are less electrons than protons, giving it an overall positive

charge,and-side,moreelectronsthanprotons,givingitanoverallnegativecharge.

BALANCEOFCHARGE

Atoms,thesmallestparticlesofmatterthatretainthepropertiesof thematter, aremadeof

protons,electrons,andneutrons. haveapositivecharge; haveanegative

chargethatcancelstheproton'spositivecharge. areparticlesthataresimilartoa

protonbuthaveaneutralcharge.Therearenodifferencesbetweenpositiveandnegative

charges except that particles with the same charge each other and particles with

oppositecharges eachother. Ifasolitarypositiveprotonandnegativeelectronare

placedneareachothertheywillcometogethertoformahydrogenatom.Thisrepulsionand

attraction (forcebetweenstationarychargedparticles) isknownasthe

and extends theoretically to infinity, but is diluted as the distance between particles

increases.

Bothatomsandtheuniversehavea chargeoverallandcomewiththesamenumberofprotonsandelectrons.Whenanatomhasoneormoremissingelectronsitisleftwitha

charge,andwhenanatomhasatleastoneextraelectronithasa charge.

Havingapositiveor anegativechargemakesanatoman .Atomsonlygainand lose

protons andneutrons through fusion, fission, and radioactive decay. Although atomsare

made of many particles and objects aremade of many atoms, they behave similarly to

chargedparticlesintermsofhowtheyrepelandattract.

Inan theprotonsandneutronscombinetoformatightlyboundnucleus.Thisnucleus

issurroundedbyavastcloudofelectronscirclingitatadistancebutheldneartheprotons

byelectromagneticattraction(theelectrostaticforcediscussedearlier).Thecloudexistsasa

seriesofoverlapping inwhichtheinner bandsarefilledwithelectrons

andaretightlyboundtotheatom.Theouter bandscontainnoelectronsexcept
http://en.wikipedia.org/wiki/protonshttp://en.wikipedia.org/wiki/electronshttp://en.wikipedia.org/wiki/neutronshttp://en.wikipedia.org/wiki/Nuclear_fusionhttp://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Nuclear_fusionhttp://en.wikipedia.org/wiki/neutronshttp://en.wikipedia.org/wiki/electronshttp://en.wikipedia.org/wiki/protons


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thosethathaveacceleratedtotheconductionbandsbygainingenergy.Withenoughenergy

anelectronwillescapeanatom(comparewiththeescapevelocityofaspacerocket).When

anelectronintheconductionbanddeceleratesandfallstoanotherconductionbandorthe

valencebandaphotonisemitted.Thisisknownasthe .

When electrons travel back and forth between conduction bands emitting

synchronizedphotons.

Whentheconductionandvalencebandsoverlap,theatomisa andallowsforthe

freemovementof electrons.Conductorsaremetalsandcanbethoughtofasabunchof

atomicnucleisurroundedbyachurning"seaofelectrons".

Whenthereisalargeenergylevelgapbetweentheconductionandvalencebands,theatom

isan ;ittrapselectrons.Manyinsulatorsarenon-metalsandaregoodatblocking

theflowofelectrons.

When there isasmallenergy level gap between the conductionand valence bands, the

atomisa .Semiconductorsbehavelikeconductorsandinsulators,andwork

usingtheconductionandvalencebands.Theelectronsintheoutervalencebandareknown

as .Theybehavelikepositivechargesbecauseofhowtheyflow.Insemiconductors

electrons collidewith thematerial and theirprogress ishalted. Thismakes the electronshavean thatislessthantheirnormalmass.Insomesemiconductorsholes

havealargereffectivemassthantheconductionelectrons.

Electronicdevicesarebasedontheideaofexploitingthedifferencesbetweenconductors,

insulators, and semiconductors but also exploit known physical phenomena such as

electromagnetismandphosphorescence.

CONDUCTORS

Inaconductortheelectronsofanobjectarefreetomovefromatomtoatom.Duetotheirmutualrepulsion(calculableviaCoulomb'sLaw),thevalenceelectronsareforcedfromthe

centeroftheobjectandspreadoutevenlyacrossitssurfaceinordertobeasfarapartas

possible.ThiscavityofemptyspaceisknownasaFaradayCageandstopselectromagnetic

radiation,suchascharge,radiowaves,andEMPs (Electro-MagneticPulses)fromentering

andleavingtheobject.IfthereareholesintheFaradayCagethenradiationcanpass.

One of the interesting things todowithconductors isdemonstrate the transfer ofcharge

betweenmetalspheres.Startbytakingtwoidenticalandunchargedmetalsphereswhichare

eachsuspendedbyinsulators(suchasapiece.Thefirststepinvolvesputtingsphere1next

tobutnottouchingsphere2.Thiscausesalltheelectronsinsphere2totravelawayfrom

sphere1tothefarendofsphere2.Sosphere2nowhasanegativeendfilledwithelectrons

andapositiveendlackingelectrons.Nextsphere2isgroundedbycontactwithaconductor

connectedwiththeearthandtheearthtakesitselectronsleavingsphere2withapositive

charge.Thepositivecharge(absenceofelectrons)spreadsevenlyacrossthesurfacedueto

itslackofelectrons.Ifsuspendedbystrings,therelativelynegativelychargedsphere1will

attracttherelativelypositivelychargedsphere2.

INSULATORS

Inan insulator theelectronsof anobjectarestuck.Thisallowscharge tobuild uponthe

surface of the object by way of the turboelectric effect. The turboelectric effect (rubbing

electricityeffect) involvesthe exchangeofelectronswhen twodifferent insulatorssuchas
http://en.wikibooks.org/wiki/Modern_Physics:Coulomb%27s_Law_and_the_Electric_Fieldhttp://en.wikibooks.org/wiki/Electronics/Signal_Propagationhttp://en.wikibooks.org/wiki/Electronics/Signal_Propagationhttp://en.wikibooks.org/wiki/Modern_Physics:Coulomb%27s_Law_and_the_Electric_Field


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glass,hardrubber,amber,oreventheseatofone'spants,comeintocontact.Thepolarity

andstrengthof thecharges produceddiffer according to thematerial compositionand its

surfacesmoothness.Forexample,glassrubbedwithsilkwillbuildupacharge,aswillhard

rubberrubbedwithfur.Theeffectisgreatlyenhancedbyrubbingmaterialstogether.

Van de Graff generator: A charge pump (pump for electrons) that generates

electricity.InaVandeGraffgenerator,aconveyorbeltusesrubbingtopickupelectrons,

whicharethendepositedonmetalbrushes.Theendresultisachargedifference.

Becausethematerialbeingrubbedisnowcharged,contactwithanunchargedobjectoran

objectwiththeoppositechargemaycauseadischargeofthebuilt-upstaticelectricitybyway

ofaspark.Apersonsimplywalkingacrossacarpetmaybuildupenoughchargetocausea

sparktotraveloveracentimeter.Thesparkispowerfulenoughtoattractdustparticlesto

cloth,destroyelectricalequipment,ignitegasfumes,andcreatelightning.Inextremecases

thesparkcandestroyfactoriesthatdealwithgunpowderandexplosives.Thebestwayto

remove static electricity isbydischarging it throughgrounding.Humid air will alsoslowly

discharge static electricity. This isone reasonwhy cells and capacitors lose charge over

time.

Note:Theconceptofaninsulatorchangesdependingontheappliedvoltage.Airlooks likean insulator whena low voltage isapplied. But itbreaks downasan insulator,becomes

ionized, at about ten kilovolts per centimeter. A person could put their shoe across the

terminalsofacarbatteryanditwouldlooklikeaninsulator.Butputtingashoeacrossaten

kilovoltpowerlinewillcauseashort.

QUANTITYOFCHARGE

Protons and electrons haveoppositebut equalcharge. Because in almost all cases, the

chargeonprotonsorelectronsisthesmallestamountofchargecommonlydiscussed,the

quantity of charge of one proton is considered one positive elementary charge and thecharge of one electron is one negative elementary charge. Because atoms and such

particles are sosmall, and charge inamountsofmulti-trillionsofelementarychargesare

usuallydiscussed,amuchlargerunitofchargeistypicallyused.Thecoulombisaunitof

charge, which can be expressed as a positive or negative number, which is equal to

approximately 6.24151018 elementary charges. Accordingly, an elementary charge is

equal to approximately 1.60210-19 coulombs. The commonly used abbreviation for the

coulombisacapitalC.TheSIdefinitionofacoulombisthequantityofchargewhichpasses

apointoveraperiodof1second(s)whenacurrentof1ampere(A)flowspastthatpoint,

i.e.,C=AsorA=C/s.Youmayfindithelpfulduringlaterlessonstoretainthispicturein

yourmind (even though youmay not recall the exactnumber). Anampere is oneof thefundamental units in physics from which various other units are defined, such as the

coulomb.

FORCEBETWEENCHARGES:COULOMB'SLAW

Therepulsiveorattractiveelectrostaticforcebetweenchargesdecreasesasthechargesare

located further fromeachotherby thesquareofthedistancebetweenthem.Anequation

calledCoulomb's lawdeterminestheelectrostaticforcebetweentwochargedobjects.The

followingpictureshowsachargeqatacertainpointwithanotherchargeQatadistanceofr

awayfromit.ThepresenceofQcausesanelectrostaticforcetobeexertedonq.
http://en.wikibooks.org/wiki/Electronics/Cellshttp://en.wikibooks.org/wiki/Electronics/Capacitorshttp://en.wikipedia.org/wiki/SIhttp://en.wikibooks.org/wiki/Electronics/Voltage%2C_Current%2C_and_Powerhttp://en.wikipedia.org/wiki/amperehttp://en.wikipedia.org/wiki/amperehttp://en.wikibooks.org/wiki/Electronics/Voltage%2C_Current%2C_and_Powerhttp://en.wikipedia.org/wiki/SIhttp://en.wikibooks.org/wiki/Electronics/Capacitorshttp://en.wikibooks.org/wiki/Electronics/Cells


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ThemagnitudeoftheelectrostaticforceF,onachargeq,duetoanotherchargeQ,equals

Coulomb'sconstantmultipliedbytheproductofthetwocharges(incoulombs)dividedbythe

squareofthedistancer,between thechargesqandQ.HereacapitalQandsmallqare

scalarquantitiesusedforsymbolizingthetwocharges,butothersymbolssuchasq1andq2

havebeenusedinothersources.Thesesymbolsforchargewereusedforconsistencywith

theelectricfieldarticleinWikipediaandareconsistentwiththeReferencebelow.

F = magnitude of electrostatic force on charge q due to another charge Q

r = distance (magnitude quantity in above equation) between q and Q

k=Coulomb'sconstant=8.9875109Nm2/C2infreespace

The value of Coulomb's constant given here is such that the preceding Coulomb's Law

equation will work if both qandQaregiven in units of coulombs, r inmeters, andF in

newtonsandthereisnodielectricmaterialbetweenthecharges.Adielectricmaterialisone

thatreducestheelectrostaticforcewhenplacedbetweencharges.Furthermore,Coulomb's

constantcanbegivenby:

where =permittivity.Whenthereisnodielectricmaterialbetweenthecharges(forexample,

infreespaceoravacuum),

=8.8541910-12C2/(Nm2).

Air isonlyveryweaklydielectricand thevalueabove for willworkwell enoughwithair

betweenthecharges.Ifadielectricmaterialispresent,then

whereisthedielectricconstantwhichdependsonthedielectricmaterial.Inavacuum(free

space),=1andthus=0.Forair,=1.0006.Typically,solidinsulatingmaterialshave

valuesof>1andwillreduceelectricforcebetweencharges.Thedielectricconstantcan

alsobecalledrelativepermittivity,symbolizedasr

Highlychargedparticlesclosetoeachotherexertheavyforcesoneachother;ifthecharges

arelessortheyarefartherapart,theforceisless.Asthechargesmovefarenoughapart,

theireffectoneachotherbecomesnegligible.

Any force on an object is a vector quantity. Vector quantities such as forces arecharacterizedbyanumericalmagnitude(i.e.basicallythesizeoftheforce)andadirection.
http://en.wikibooks.org/wiki/Scalarhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikibooks.org/wiki/Vectorhttp://en.wikibooks.org/wiki/Vectorhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikibooks.org/wiki/Scalar


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Thepotentialdifferencebetweentwotestpoints resultingfrom thedistributionof

chargeinthecircuit,usuallymeasuredinvolts.

Netamountofcharge(numberofelectrons)flowingpastaspecifiedpoint,usually

measured inAmps. In typical components and systems the quantity ofelectrons isquite

largeandtheaggregatechargeflowisreferredtoaselectricity.

Energygiveninacertainamountoftime,usuallymeasuredinwatts.

Oppositechargesattractwhilesimilarchargesrepel.

Whenelectricitypassesthroughawireitcreatesamovingmagneticfieldaround

thewire.ThetypicalunitofmeasureisHenrys.

Whenelectricfieldsorchargedistributionsarecreatedinaphysicalsystem

that stores recoverable energy, characteristics of the physical components which affect

calculationoftheelectricalquantitiesaredefinedascapacitance.ThebaseunitofmeasureisFarads,howevermicrofarads(F),areusedmuchmoreoften.

Whenpotentialdifferencecreatesmovementofelectronsbetweentwopoints,

someofthepotentialenergyformerlyavailableinthesystemisirreversiblytransferredfrom

theelectricfieldortheelectronsmovingthroughthecomponentviacollisionswithatomsand

moleculeswithinthematerial.Ohm'sLaw,V=IR,definesresistanceasR=V/IwhereVisthe

voltagedifferenceappliedacrossthecomponent,IistheresultingcurrentflowinAmps,and

R isaconstantcreatedbycharacteristics of the componentwhich iscalculated from the

measuredvoltagelossofthemeasuredcurrentpassingthroughthecomponent.

Achargedparticlesuchasaprotonorelectronmay"feel"anelectricalforceonitinacertain

environment.Thisforceistypicallyduetothepresenceofotherchargesnearby.Theforce

willhaveadirectionandmagnitude,andcanberepresentedbyavector.(Avectorissimply

aquantitythatrepresentsthedirectionandmagnitudeofsomething.)Themagnitudeofthe

forcedependsonthechargeoftheparticle,thechargeontheparticlesaroundit,andhow

closeorfarawaytheyare:Highlychargedparticlesclosetoeachotherexertheavyforces

on each other; if the charges are less, or they are farther apart, the force is less. The

directionoftheforcedependsonthelocationofthesurroundingcharges.

Indescribingtheelectricalenvironmentatthatlocation,it issaidthereisanelectricfieldat

thatlocation.Theelectricfieldisdefinedastheforcethatasingleunitofchargewouldfeel

atthatlocation.Insomesystemsofmeasurement,theunitofchargeisthechargeofasingle

proton;inothersitisthecoulomb.Acoulombisthechargeof6.241018protons

Therelationshipbetweenforceandelectricfieldforasinglechargedparticleisgivenbythe

followingequation:

Theboldlettersindicatevectorquantities.Thismeansthatachargeq,inanelectricfieldE,

havingacertaindirectionandmagnitudeE,wouldhaveaforceFonit,inthesamedirection

andwithamagnitudeF.Consideringonly themagnitudes, thefollowingwouldresult fromthedefinition.


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E=F/qtheseareallmagnitudesornumericalquantities

The net electric fieldE,ata location isdue to the presenceofall otherchargesnearby,

similartothenetelectricforceF,iftherewasachargeqatthatlocation.Thecontributionof

oneoftheseotherchargestothetotal(ornet)electricfieldisavectorEcontribution,which

for apointcharge canbederivedfromCoulomb's Law.Distributionsofcharge density in

variousshapesmayalsoyieldvectorEcontributionstothetotalelectricfield,tobeaddedin

asvectorquantities.Practicallyspeaking,mostelectricians,electricalengineers,andother

electricalcircuitbuildersandhobbyistsseldomdothesesortsofelectricfieldcalculations.

Electricfieldcalculationsofthissortaremoreofatheoreticalphysicsorspecialapplications

problem,sothesecalculationsareomittedhereinfavorofmoreapplicablematerial.Seelink

forsuchinformationonelectricfieldformulas.

Thereisanelectrical forceona chargeonly if thereis achargesubject tothe forceata

locationinanelectric field.However,even ifthere isnosuchchargesubject totheforce,

therecouldstillbeanelectricfieldatapoint.Thismeansthatanelectricfieldisapropertyof

a locationorpoint in spaceand its electrical environment,whichwoulddeterminewhata

chargeqwould"feel"ifitwerethere.

Now,amicro-physicsreview:Workiscausingdisplacement(ormovement)ofanobjector

matteragainstaforce.Energyistheabilitytoperformworklikethis.Energycanbekinetic

energyorpotentialenergy.Kineticenergy istheenergyamasshasbecauseitismoving.

Potential energy in an object, in matter, in a charge or other situation has the ability to

performworkortobeconvertedintokineticenergyoradifferentkindofpotentialenergy.

Areasonwhyaparticleorachargemayhavepotentialenergycouldbebecauseitislocated

atapointinaforcefield,suchasagravitationalfield,electricfield,ormagneticfield.Inthe

presenceof suchafield,gravityor electricormagneticforcescouldcause theparticle or

charge to move faster or move against resistive forces, representing a conversion ofpotential energy to kinetic energy or work. The amount of potential energy it haswould

depend on its location.Moving fromone location toanother couldcause a change in its

potential energy.

For example, an object near the surface of the earth placed high would have a certain

amountofgravitationalpotentialenergybasedon itsmass, location (heightoraltitude) in

and strengthof the earth'sgravitational field. If the object were to drop from this location

(height)toanewlowerlocation,atleastsomeofitsgravitationalpotentialenergywouldbe

converted to kinetic energy, resulting in the object moving down. The difference in

gravitational potential energy could be calculated from one location to another, but

determiningtheabsolutepotentialenergyoftheobjectisarbitrary,sogroundlevelischosen

arbitrarilyas theheightwhere itsgravitational potential energyequalszero. Thepotentialenergyatallotherheightsisdeterminedfromthemassoftheobject,locationrelativetothe

groundlevel,andstrengthofthegravitationalfield.

Allenergyvaluesarenumericalorscalarquantities,notvectors.

Somewhat similarly, a charged particle at a certain point or location in an electrical

environment(i.e.anelectricfield)wouldhaveacertainamountofelectricpotentialenergy

basedonitscharge,location,andtheelectricfieldthere,whichcouldbebasedonquantity

andlocationsofallotherchargesnearby.Ifthechargeweretomovefromthislocationtoa

newlocationorpoint,itcouldcauseachangeinitselectricpotentialenergy.Thisdifferenceinelectricpotentialenergyinthechargeparticlewouldbeproportionaltoitschargeandit
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couldbeanincreaseoradecrease.Frommeasurementsandcalculations,onemaybeable

todeterminethisdifferenceinelectricpotentialenergy,butcomingupwithanabsolutefigure

for its potential isdifficult and typically not necessary. Therefore, inamanner somewhat

similar to gravitational potential energy, an arbitrary location or point nearby, often

somewhere intheelectric circuit inquestion, ischosen tobethepointwherethe electric

potential energy would be zero, if the charge were there. Often the wiring, circuit, or

appliancewillbeconnectedtotheground,sothisgroundpointisoftenchosentobethezero

point.Theelectricpotentialenergyatallother points isdetermined relativeto theground

level.TheSIunitofelectricpotentialenergyis,ofcourse,thejoule.

Becausetheelectricpotentialenergyofachargedparticle(orobject)isproportionaltoits

chargeandotherwisesimplydependentonitslocation(pointwhereit'sat),ausefulvalueto

use iselectricpotential. Electric potential (symbolizedbyV) at a point is defined as the

electricpotentialenergy(PE)perunitpositivecharge(q)thatachargewouldhaveatthat

givenpoint(location).Atapointa,theelectricpotentialataisgivenby:

Va=(PEofchargeata)/qSomewhatanalogouslytoanelectricfield,electricalpotentialisapropertyofalocationand

theelectricalconditionsthere,whetherornotthereisachargepresenttheresubjecttothese

conditions.Ontheotherhand,electricpotentialenergyismoreanalogoustoelectricforcein

thatforittobepresent,thereshouldbeasubjectchargedparticleorobjectwhichhasthat

energy.Electricpotentialisoftensimplycalledpotentialbyphysicists.BecausetheSIunitof

electricpotentialenergyisthejouleandbecausetheSIunitofchargeisthecoulomb,theSI

unitforelectricpotential,thevolt(symbolizedbyV),isdefinedasajoulepercoulomb(J/C).

Becauseelectricpotentialenergyisbasedonanarbitrarypointwhereitsvalueissetatas

zero,thevalueofelectricpotentialatagivenpointisalsobasedonthissamearbitraryzero

point(referencepointwherethepotentialissetatzero).Thepotentialatagivenpointaisthenthedifferencebetweenpotentialsfrompointatothezeropoint,oftencalledaground

node(orjustground).

Calculationsofelectricpotential energyorelectricpotentialbasedonCoulomb's Laware

sometimestheoreticallypossible,suchasmightbeforelectricfieldcalculations,butagain

these are of mostly theoretical interest and not often done in practical applications.

Therefore,suchcalculationsarealsoomittedhereinfavorofmoreapplicablematerial.

Often it isof interest tocomparethepotentialsat twodifferentpoints,whichwemay call

pointaandpointb.Thentheelectricpotentialdifferencebetweenpointsaandb(Vab)would

bedefinedastheelectricpotentialatbminustheelectricpotentialata.

Vab=Vb-Va

Theunitforelectricpotentialdifferenceisthevolt,thesameasforelectricpotential.Electric

potential difference is often simply called potential difference by physicists. Under direct

current (DC) conditions and at any one instant in time under alternating current (AC),

potential andpotentialdifference arenumerical orscalarquantities,notvectors,andthey

canhavepositiveornegativevalues.

iselectricpotentialexpressedinvolts.Similarly, potential differenceexpressed in

voltsisoftencalled oroftenreferredtoasvoltageacrosstwopointsor

across an electrical component. The terms electric potential, potential, and potentialdifferencearetermsmoreoftenusedbyphysicists.Sincethesequantitiesarealmostalways
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expressed in volts (or some related unit such as milli volts), engineers, electricians,

hobbyists, and common people usually use the term voltage instead of potential.

Furthermore, inpracticalapplications,electrical force,electricfield,andelectricalpotential

energyofchargedparticlesarenotdiscussednearlyasoftenasvoltage,power,andenergy

inamacroscopicsense.

Additionalnote:Thefollowingexplainswhyvoltageis"analogous"tothepressureofafluid

inapipe(although,ofcourse,itisonlyananalog,notexactlythesamething),anditalso

explains the strange-sounding "dimensions" of voltage. Consider the potential energy of

compressedairbeingpumpedintoatank.Theenergyincreaseswitheachnewincrementof

air.Pressureisthatenergydividedbythevolume,whichwecanunderstandintuitively.Now

considertheenergyofelectriccharge(measuredincoulombs)beingforcedintoacapacitor.

Voltage is that energy per charge, so voltage is analogous to a pressure-like sort of

forcefulness.Also,dimensionalanalysistellsusthatvoltage("energypercharge")ischarge

perdistance,thedistancebeingbetweentheplatesofthecapacitor

Whenanelectriccircuitisoperatingin DirectCurrent (DC)mode,allvoltagesandvoltagedifferences in the circuit are typically constant (do not vary)with time.When a circuit is

operating under Alternating Current (AC) conditions, the voltages in the circuit vary

periodicallywithtime;thevoltagesareasinusoidalfunctionoftime,suchasV(t)=asin(bt)

withconstantaandb,orsomesimilarfunction.Thenumberoftimestheperiodrepeats(or

"cycles") per unit time iscalled the frequencyofV(t).UnderDC conditionsoratanyone

instantintimeunderAC,potential(orvoltage)andpotentialdifference(orvoltagedifference)

are numerical or scalar quantities, not vectors, and they can have positive or negative

values. However, in AC mode, the overall function of voltage with time V(t), can be

expressedasacomplexnumberoraphasorforagivenfrequency.Thefrequencycanbe

expressed in cycles per second or simply sec-1, which is called (Hz) in SI units.TypicalcommercialelectricpowerprovidedintheUnitedStatesisACatafrequencyof60

Hz.

Ground isshownonelectronicsdiagrams, but it isn't really acomponent. It issimply the

nodewhichhasbeenassigneda voltageofzero. It is representedbyoneof thesymbols

below. Technically, any single node can beassigned asground, and other voltagesare

measured relative to it.However, the convention is toonly assign it inone of two ways,

relatedtothetypeofpowersupply.Inasinglesupplysituation,suchasacircuitpoweredby

a single battery, the ground point is usually defined as themore negative of the power

source's terminals. Thismakesall voltages in the circuit positivewith respect to ground

(usually),andisacommonconvention.Forasplit-supplydevice,suchasacircuitdrivenby

acenter-tappedtransformer,usuallythecentervoltageisdefinedasground,andthereare

equalandroughlysymmetricalpositiveandnegativevoltagesinthecircuit.

Signal

Ground

Chassis

Ground

Earth

Ground
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Groundforasignal.Sincewireshaveacertainamountofresistancetothem,groundpoints

inacircuitaren'tallatexactlythesamevoltage.Itisimportantinpracticalcircuitdesignto

separatethepowersupplygroundfromthesignalgroundfromtheshieldingground,etc.In

circuitswhereminimumnoiseisespeciallyimportant,powerregulatorcircuitryshouldhave

thickwiresortracesconnectingthegrounds,inasequence fromthepower supply tothe

"cleanest"groundattheoutputofthefiltersofthepowersupply,whichwillthenbea"star

point"forthegroundsofthesignalcircuitry.

Adirectconnectiontothechassisofthedevice.This isused forEMIshieldingandalsofor

safetygroundinlineACpowereddevices.

Usedinradioorpowerdistributionsystems,aconnectiontotheEarthitself.Alsotheother

endoftheconnectionfor the safetyground,sincethepower linevoltagewillseekapath

throughtheEarthbacktothepowerlinesupplystation.Thiswastheoriginalusageofthe

word"ground",andthemoremodernmeaningofthewordwouldhavebeencalleda"floatingground".

Theearthgroundsymbolandsignalgroundsymbolareofteninterchangedwithoutregardto

their original meanings. As far as signal-level electronics (and this book) is concerned,

groundalmostalwaysmeansasignalgroundorfloatingground,notconnectedtotheearth

itself.

oftencalledjustcurrent,isthemovementofchargeinaconductor(suchas

awire)orinto,outof,orthroughanelectricalcomponent.Currentisquantifiedasarateof

positivechargemovementpastacertainpointorthroughacross-sectionalarea.Simplyput,

current isquantified aspositive charge per unit time.However, sincecurrent isa vector

quantity, the direction inwhich the current flows is still important.Current flow inagiven

directioncanbepositiveornegative;thenegativesignmeansthatpositivechargesmove

opposite of the given direction. The quantity of current at a certain point is typically

symbolizedbyacapitalorsmall letter Iwithadesignationwhichdirectionthecurrent I is

moving.TheSI unitofcurrentistheampere(A),oneofthefundamentalunitsofphysics.

See ampere for thedefinitionofampere.Sometimes, ampere is informallyabbreviated to

amp. The definition of a coulomb (C), the SI unit of charge, is based on an ampere. A

coulomb is the amount of positive charge passinga pointwhen a constant one ampere

currentflowsbythepointforonesecond.ThesecondistheSIunitoftime.Inotherwords,acoulombequalsanampere-second(As).Anampereisacoulombpersecond(C/s).

Typically,currentisinametalandconstitutesmovementofelectronswhichhavenegative

charge;however,peopleinitiallythoughtthatcurrenthadapositivecharge.Theresultisthat

even though current is the flowofnegativeelectronsand flows from the negative to the

positiveterminalofabattery,whenpeopledocircuitanalysistheypretendthatcurrentisa

flowofpositiveparticlesandflowsfromthepositivetothenegativeterminalofabattery(or

otherpowersource).Actually,itismorecomplicatedthanthis,sincecurrentcanbemadeup

ofelectrons,holes,ions,protons,oranychargedparticle.Sincetheactualchargecarriers
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areusuallyignoredwhenanalyzingacircuit,current issimplifiedandthoughtofasflowing

frompositivetonegative,andisknownasconventionalcurrent.

Analogytopebbletossing:IhavepebblesandIamthrowingthemintoabasket.Indoingthis

thebasketgainspebblesandIlosepebbles.Sothereisanegativecurrentofpebblestothe

basket because it is gaining pebbles, and there is a positive current of pebbles to me

because I am losing pebbles. In pebble tossing the currents have equal strength but in

oppositedirections.

CurrentIisrepresentedinamperes(A)andequalsxnumberofy

Powerisenergyperunitoftime.TheSIunitforpoweristhe (W)whichequalsa

(J/s),withjoulebeingtheSIunitfor andsecondbeingtheSIunitfor .

When somebody plugs an appliance into a receptacle to use electricity to make that

appliancefunction,thatpersonprovideselectricalenergyfortheappliance.Theappliance

usually functions by turning that electrical energy into heat, light, or work or perhapsconvertsitintoelectricalenergyagaininadifferentform.Ifthissituationisongoing,itissaid

thatthereceptacleorelectricpowercompanydeliverspowertotheappliance.Thecurrent

fromthereceptaclegoinginandoutoftheapplianceeffectivelycarriesthepowerandthe

applianceabsorbsthepower.

Multiplyingaunitofpowerbyaunitoftimewouldresultinaunitthatrepresentsaquantityof

energy.Therefore,multiplyingakilowattbyanhourgivesakilowatt-hour(kWh),aunitoften

usedbyelectricalpowercompaniestorepresentanamountofelectricalenergygeneratedor

providedtoconsumers.

Fordirectcurrent(DC),powerPcanbecalculatedbymultiplyingthevoltageandcurrent,

whentheyareknown.

P=VI

Notethatenergy/chargeismultipliedbycharge/timetogiveenergy/time.Atanyonepointin

timetinalternatingcurrent(AC)circuitry,powerP(t)equalsvoltageV(t)timescurrentI(t).

P(t)=V(t)I(t)atanyonetimet

CalculationsofACpoweraveragedovertimewillbediscussedunderACpower.

An electronic is a system in which conventional current flows from the positive

terminalofasource,throughaload,tothenegativeterminalofthesource.

Ashortcircuitisanothernameforanode,althoughitusuallymeansanunintentionalnode.

Hascurrentthroughitbutnovoltageacrossit.

Haspotentialacrossitbutnocurrentthroughit.


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Theoretical circuit connection (wire) has no resistance or inductance. Real wires always

have voltage over them if there is current flowing through them (resistance). On high

frequencies there are markable voltage potentials over wire links if there is flowing

alternatingcurrentthroughwires(inductancelikeininductors).

Twomaterials with a voltage difference between them.This causes current to flow

whichdoeswork.Electronstravelfromthecathode,dosomework,andareabsorbedbythe

anode.

Destinationofelectrons.

Sourceofelectrons.

Anatomwithanimbalanceofelectrons.thecellrunsandelectronsaredepletedatthecathodeandaccumulateatthe

anode.Thiscreatesareversevoltagewhichstopstheflowofelectrons.

oncethecellrunsoutofjuiceitisdead.

abletorunthecellbackwards.

thecellcanberunbackwardsbytheapplicationofelectricity.

humidairwilldischargecells.

cellsareusuallymadeoftoxicorcorrosivesubstances,forexampleleadandsulphuricacid.

Theyhavebeenknowntoblowup.

Whatistherelationshipbetweenvoltageandelectronegativity?

isaconceptinchemistryusedtomeasureandpredicttherelativelikilihood

ofachemical reactioncausingelectronsto shift fromonechemicalto anotherresulting in

ionsandmolecularbonds.Abatterycell operatesbyallowing twochemicals to reactand

supply ions to theanodeand cathode.When the supply of a reactant is consumed, the

batteryisdead.Itnolongerproducesdifferentelectricalpotentialattheanodeandcathode

drivenbythechemicalreaction.

Voltageistheelectricalpotentialofapointduetosurroundingmeasurableelectriccharge

distributions and points as calculated by application Coulomb's Law. Voltage difference

betweentwopointsconnectedbyaconductorresultsinelectronflow.

RESISTORS


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Aresistorisablockofmaterialthatlimitstheflowofcurrent.Thegreatertheresistance,the

lowerthecurrentwillbe.Sinceconductorshavean"electronsoup"aroundtheatoms,they

behave like a wide pipe filled with water, and have low resistance to a flow of water.

Insulators,ontheotherhand,behavemorelikeatinypipe,orasponge-filledpipe.While

theyareporousandallowcurrenttoflow,aspongethatismoredenseandhaslessholes

willhaveahigher resistanceanda smallerflowof current,if thepressurepushingon the

wateristhesame.

Resistancecanvaryfromverysmalltoverylarge.Asuperconductorhaszeroresistance,

whilesomethingliketheinputtoanop-ampcanhavearesistancenear1012,andeven

higher resistances arepossible. Formostmaterials, as temperature increases resistance

tendstoincreaseaswell.Resistanceconvertselectricalenergyintoheat.Resistorswhich

dissipate largeamountsofpowerarecooledso thattheyarenot destroyed, typicallywith

finnedheatsinks.

Resistorshavetwo leads (pointsofcontact) towhich the resistorcanbe connected toan

electricalcircuit.Asymbolforaresistorusedinelectricalcircuitdiagramsisshownbelow.Thetwoblackdotsindicatethepointsofcontactfortheresistor.Theratioofthevoltageto

currentwillalwaysbepositive,sinceahighervoltageononesideofaresistorisapositive

voltage,and a currentwill flow from the positiveside to the negative side, resulting in a

positivecurrent.Ifthevoltageisreversed,thecurrentisreversed,leadingagaintoapositive

resistance.

TheratioofvoltagetocurrentisreferredtoasOhm'sLaw,andisoneofthemostbasiclaws

thatgovernelectronics.

(Ohm'slawisnotnecessarilyexpressedinthisway,butdoesexpressthatanoppositionis

equivalenttotheratioofacausetotheeffect)

Unlikesomeelectricalcomponents,itdoesnotmatterwhichwayyoupluginresistors;they

have no polarity. Also, asmost electronics components have internal resistance, this is

sometimesshownbyputtingaresistorinserieswiththecomponenttotaketheresistance

intoaccount.

Resistanceisgiveninohms()where:

Anohmis theamountof resistancewhichpassesoneampereofcurrentwhenaonevolt

potentialisplacedacrossit.(Theohmisactuallydefinedastheresistancewhichdissipates

onewattofpowerwhenoneampereofcurrentispassedthroughit.)

Lowervaluedresistorsaresometimesreferredtoasa load.Aresistordissipatesenergyas

electronsstriketheatomsandtransfertheenergytotheresistormaterial.Aloadisdefined

as the power dissipated between two terminals. Usually, this is an output, and the

compositionoftheloadisunknown.Thismeasureisnotrelatedtotheconductance,whichistheinverseofresistance.ConductanceismeasuredinSiemens(S)orsometimesreferredto


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asMhos (-1).Used as an adjective, a load hasa load with ameasurable power draw

(expressedinWatts).Thepowerdrawn(load)istheamountofvoltageacrosstheterminals

multipliedbythecurrentthroughtheterminals.

Power:

AfterOhm'slawissubstitutedintotheequation

:

ForanACsignaloranykindofchangingsignal,theaveragepowerdissipatedisrelatedto

theRMSvalueofthevoltage,notthepeak-to-peakvoltage:

Forapuresinewave,therelationshipbetweenpeak-to-peakvoltageandRMSvoltageis

Soaresistorwith1VDCacrossitandanequal-valueresistorwith1VRMS=1.414VPPAC

sinusoidwillbothdissipatethesameamountofpower(heat).

Consider thedefinitionofPowerRating,below.When associating resistors toproducean

equivalentLoad,wecanhaveanequivalentresistancewhichislargerorsmallerthaneach

individualelement, dependingon the typeofassociation beingseries orparallel, but the

equivalent power ratingwill always be larger thaneach individual powerratings. Inother

words:Twoequalvalueresistorsinparallelwillhavehalftheresistancebuttwicethepowerrating.

Twoequalvalueresistorsinserieswillhavetwicetheresistanceandtwicethepowerrating.

Amanufacturedresistorisusuallylabeledwiththenominalvalue(valuetobemanufactured

to) and sometimes a tolerance. Rectangular resistors will usually contain numbers that

indicatearesistanceandamagnitude.Iftherearethreeorfournumbersontheresistor,the

firstnumbersarearesistancevalue,andthelastnumberreferstothemagnitude.Ifthereis

anRinthevalue,theRtakestheplaceofthedecimalpoint.

2003means200103=200k

600means60100=60

2R5means2.5

R01means0.01

Cylindrical resistors (axial) usually have colored bands that indicate a number and a

magnitude.Resistancebandsarenexttoeachother,withatolerancebandslightlyfarther

awayfromtheresistancebands.Startingfromtheresistancebandsideoftheresistor,each

colorrepresentsanumberinthesamefashionasthenumbersystemshownabove.


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COLORSYSTEM

Black Brown Red Orange Yellow Green Blue Violet Grey White

0 1 2 3 4 5 6 7 8 9

B.B.ROYofGreatBritainwasaVeryGoodWorker.

A gold band in the magnitude position means -1, but means a 5%

tolerance.Asilverbandinthemagnitudepositionmeans-2,butmeansa10%tolerance.

The resistanceR ofacomponent isdependentonitsphysicalcharacteristicsandcanbe

calculatedusing:

whereistheelectricalresistively(resistancetoelectricity)ofthematerial,Listhelengthof

thematerial,andAisthecross-sectionalareaofthematerial.

IfyouincreaseorLyouincreasetheresistanceofthematerial,butifyouincreaseAyou

decreasetheresistanceofthematerial.

RESISTIVELY OF THEMATERIAL

Everymaterialhasitsownresistively,dependingonitsphysicalmakeup.Mostmetalsareconductorsandhaveverylowresistively;whereas,insulatorssuchasrubber,wood,andair

allhaveveryhighresistively.Theinverseofresistivelyisconductivity,whichismeasuredin

unitsofSiemens/meter(S/m)or,equivalently.Mhos/meter.

In the following chart, it is not immediately obvioushow the unit ohm-meter is selected.

Consideringasolidblockofthematerialtobetested,onecanreadilyseethattheresistance

oftheblockwilldecreaseasitscross-sectionalareaincreases(thuswideningtheconceptual

"pipe"),andwillincreaseasthelengthoftheblockincreases(lengtheningthe"pipe").Given

a fixed length, the resistance will increase as the cross-sectional area decreases; the

resistance, multiplied by the area, will be a constant. If the cross-sectional area is held

constant,asthelengthisincreased,theresistanceincreasesinproportion,sotheresistance

dividedbythelengthissimilarlyaconstant.Thusthebulkresistanceofamaterialistypically

measuredinohmmeterssquaredpermeter,whichsimplifiestoohm-meter(-m).

Silver 1.5910-8

Copper 1.610-

Gold 1.710-8

Aluminum 2.8210-

Tungsten 5.610-

Iron 1010-


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Platinum 1110-

Lead 2210-

Nichrome1.5010- (Anickel-chromiumalloycommonlyusedinheating

elements)

Graphite ~10-

Carbon 3.510-

PureGermanium 0.6

PureSilicon 640

Common purified

water~103

Ultra-purewater ~105

Pure Gallium

Arsenide~106

Diamond ~1010

Glass 10 to10

Mica 91013

Rubber 10 to10

Organicpolymers ~1014

Sulfur ~10

Quartz(fused) 5to751016

Air veryhigh

Silver, copper,gold,andaluminumarepopularmaterials forwires,dueto low resistively.

Siliconandgermaniumareusedassemiconductors.Glass,rubber,quartzcrystal,andair

arepopulardielectrics,duetohighresistively.

Manymaterials,suchasair,haveanon-linearresistancecurve.Normalundisturbedairhas

a high resistance, but air with a high enough voltage applied will become ionized and

conductveryeasily.

Theresistivelyofamaterialalsodependsonitstemperature.Normally,thehotteranobjectis, themore resistance it has.Athigh temperatures, the resistance isproportional to the

absolute temperature. At low temperatures, the formula is more complicated, and what

countsasa highor low temperaturedependsonwhat theresistor ismade from.Insome

materials the resistively drops to zero below a certain temperature. This is known as

superconductivity,andhasmanyusefulapplications.

(Somematerials,suchassilicon,havelessresistanceathighertemperatures.)

For all resistors, the change in resistance for a small increase in temperature is directly

proportionaltothechangeintemperature.

Currentpassing througha resistorwillwarm it up. Many componentshaveheat sinks to

dissipatethatheat.Theheatsinkkeepsthecomponentfrommeltingorsettingsomethingonfire.


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unitsm2cancel:

Which,afterevaluating,givesyouafinalvalueof8.010-6,or8microohms,averysmall

resistance? The method shown above included the units to demonstrate how the unitscancelout,butthecalculationwillworkaslongasyouuseconsistentunits.

InternetHint:Googlecalculatorcandocalculationslikethisforyou,automaticallyconverting

units.Thisexamplecanbecalculatedwiththislink:[1]

Usedfor power resistors, sincethepower per volume ratiois highest.These

usuallyhavethelowestnoise.

These areeasy to produce, but usually have lots of noise because of the

propertiesofthematerial.

These resistors have thermal and voltage noise attributes that are between

carbonandwirewound.

Usefulforhighfrequencyapplications.

RESISTORJUNCTIONS

Resistors in series are equivalent to having one long resistor. If the properties of tworesistors are equivalent, except the length, the finalresistancewillbethe sumof the two

constructionmethods:

Thismeansthattheresistorsaddwheninseries.

Christmastreelightsareusuallyconnectedinseries,sothatifonelightblows,theotherswillallgoout.However,moststringshavebuiltinshuntresistorsinparalleltothebulb,sothatcurrentwillflowpasttheblownlightbulb.

Inaparallelcircuit,currentisdividedamongmultiplepaths.Thismeansthattworesistorsinparallelhavea lowerequivalent resistance thaneitherof theparallel resistors,sinceboth
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resistorsallowcurrenttopass.Tworesistorsinparallelwillbeequivalenttoaresistorthatis

twiceaswide:

Sinceconductance(theinverseofresistance)addinparallel,yougetthefollowingequation:

Forexample,two4resistorsinparallelhaveanequivalentresistanceofonly2.

To simplify mathematical equations, resistances in parallel can be represented with two

verticallines"||"(asingeometry).Fortworesistorstheparallelformulasimplifiesto:

Resistorsinparallel areevaluatedas if inamathematicalsetof "parentheses."Themost

basicgroupofresistorsinparallelisevaluatedfirst,thenthegroupinserieswiththenew

equivalentresistor,thenthenextgroupof resistorsinparallel,andsoon.Forexample,the

aboveportionwouldbeevaluatedasfollows:

RESISTOR VARIATIONS

Variableresistorsaretunable,meaningyoucanturna

dialorslideacontact andchange the resistance.Theyare usedasknobs tocontrol the

volumeofastereo,orasadimmerforalamp.Oftenabbreviatedas'pot'.Itisconstructed

likearesistor,buthasaslidingtapcontact.Potentiometersareusedas VoltageDividers.It

is rare to finda variable resistorwith only two leads.Most are potentiometerswith three

leads,evenifoneisnotconnectedtoanything.
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entirerangeofspecificationsshouldbeconsidered.Usually,exactvaluesdonotneedtobe

known,butrangesshouldbedetermined.

The nominal resistance is the resistance that can beexpected whenordering a resistor.

Finding a range for the resistance is necessary, especially when operating on signals.

Resistorsdonotcomeinallofthevaluesthatwillbenecessary.Sometimesresistorvalues

can be manipulated by shaving off parts of a resistor (in industrial environments this is

sometimesdonewithaLASERtoadjustacircuit),orbycombiningseveralresistorsinseries

andparallel.

Available resistor values typically comewith a resistance value from a so called resistor

series.Resistorseriesaresetsof standard, predefinedresistancevalues.Thevaluesare

actuallymadeupfromageometricsequencewithineachdecade.Ineverydecadethereare

supposedtobenresistancevalues,withaconstantstepfactor.Thestandardresistorvalues

withinadecadearederivedbyusingthestepfactori

roundedtoatwodigitprecision.ResistorseriesarenamedEn,accordingtotheusedvalue

ofnintheaboveformula.

nValues/DecadeStepfactoriSeries

----------------------------------------

61.47E6

121.21E12

241.10E24

481.05E48

For example, in the E12 series for n = 12, the resistance steps in a decade are, after

roundingthefollowing12values:

1.00,1.20,1.50,1.80,2.20,2.70,

3.30,3.90,4.70,5.60,6.80,and8.20

andactuallyavailableresistorsfromtheE12seriesareforexampleresistorswithanominal

valueof120or4.7k.

Amanufacturedresistorhasacertaintolerancetowhichthe resistancemaydifferfromthe

nominalvalue.Forexample,a2kresistormayhaveatoleranceof5%,leavingaresistor

withavaluebetween1.9kand2.1k(i.e.2k100).Thetolerancemustbeaccounted

forwhendesigningcircuits.Acircuitwithanabsolutevoltageof5V0.0Vinavoltagedividernetworkwithtworesistorsof2k5%willhavearesultantvoltageof5V10%(i.e.5V0.1V).

The finalresistor tolerancesare foundby taking the derivativeof the resistorvalues,and

pluggingtheabsolutedeviationsintotheresultingequation.

TheabovementionedE-serieswhichareusedtoprovidestandardizednominalresistance

values, are also coupled to standardized nominal tolerances. The fewer steps within a

decadethereare,thelargertheallowedtoleranceofaresistorfromsuchaseriesis.More

preciseresistors,outsideofthementionedE-seriesarealsoavailable,e.g.forhigh-precision

measurementequipment.Commontolerances,colorsandkeycharacters used to identify

themareforexample:

SeriesValues/DecadeToleranceColorCodeCharacterCode

--------------------------------------------------------------

E6620%[none][none]


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resistoristobeusedasathermostatinthoseranges.Thesimplifiedlinearizedformulafor

theaffectontemperaturetoaresistorisexpressedinanequation:

R=R0[1+(TT0)]

Real world resistors not only show the physical property of resistance, but also have a

certaincapacityandinductance.Thesepropertiesstarttobecomeimportant,ifa resistoris

used in some high frequency circuitry. Wire wound resistors, for example, show an

inductancewhichtypicallymakesthemunusableabove1kHz.

Resistorscanbepackagedinanywaypossible,butaredividedintosurfacemount,through

hole,solderingtagandafewmoreforms.Surfacemountisconnectedtothesamesidethat

the resistor ison. Throughhole resistors have leads (wires) that typically go through the

circuit boardand are soldered to the boardon the side opposite the resistor, hence the

name.Resistors with leads are also used in point-to-point circuitswithout circuit boards.Solderingtagresistorshavelugstosolderwiresorhighcurrentconnectorsonto.

Usualpackagesforsurfacemountresistorsarerectangular,referencedbyalengthanda

widthinmils(thousandsofaninch).Forinstance,an0805resistorisarectanglewithlength

.08"x.05",withcontacts(metalthatconnectstotheresistor)oneitherside.Typicalthrough

holeresistorsarecylindrical,referencedeitherbythelength(suchas0.300")orbyatypical

powerratingthatiscommontothelength(a1/4Wresistoristypically0.300").Thislength

doesnotincludethelengthoftheleads.

CAPACITORS

Acapacitor(historicallyknownasa"condenser")isadevicethatstoresenergyinanelectric

field,byaccumulatinganinternalimbalanceofelectriccharge.Itismadeoftwoconductors

separatedbyadielectric(insulator).Usingthesameanalogyofwaterflowingthroughapipe,

acapacitorcanbethoughtofasatank,inwhichthechargecanbethoughtofasavolumeof

waterinthetank.Thetankcan"charge"and"discharge"inthesamemannerasacapacitor

doestoanelectriccharge.Amechanicalanalogyisthatofaspring.Thespringholdsa

chargewhenitispulledback.

Whenvoltageexistsoneendofthecapacitorisgettingdrainedandtheotherendisgetting

filledwithcharge.Thisisknownascharging.Chargingcreatesachargeimbalancebetweenthe twoplatesandcreatesareversevoltage thatstopsthecapacitor fromcharging.Asa


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result, when capacitors are first connected to voltage, charge flows only to stop as the

capacitor becomes charged. When a capacitor is charged current stops flowing and it

becomesanopencircuit.Itisasifthecapacitorgainedinfiniteresistance.

Youcanalsothinkofacapacitorasafictionalbatteryinserieswithafictionalresistance.

Starting the charging procedure with the capacitor completely discharged, the applied

voltageisnotcounteractedbythefictionalbattery,becausethefictionalbatterystillhaszero

voltage,andthereforethechargingcurrentisatitsmaximum.Asthechargingcontinues,the

voltageof the fictional battery increases, and counteracts the appliedvoltage,sothat the

chargingcurrentdecreasesasthefictionalbattery'svoltageincreases.Finallythefictional

battery'svoltageequalstheappliedvoltage,sothatnocurrentcanflowinto,noroutof,the

capacitor.

Justasthecapacitorchargesitcanbedischarged.Thinkofthecapacitorbeingafictional

battery that supplies at first a maximum current to the "load", but as the discharging

continuesthevoltageof thefictionalbatterykeepsdecreasing,andthereforethedischarge

currentalsodecreases.Finallythevoltageofthefictionalbatteryiszero,andthereforethe

dischargecurrentalsoisthenzero.

This is not the same asdielectric breakdown where the insulator between the capacitorplatesbreaksdownanddischargesthecapacitor.Thatonlyhappensat largevoltagesand

the capacitor is usually destroyed in the process. A spectacular example of dielectric

breakdownoccurswhenthetwoplatesofthecapacitorarebroughtintocontact.Thiscauses

allthechargethathasaccumulatedonbothplatestobedischargedatonce.Suchasystem

ispopularforpoweringlaserswhichneedlotsofenergyinaverybriefperiodoftime.

CAPACITANCE

Thecapacitanceofacapacitorisaratiooftheamountofchargethatwillbepresentinthe

capacitorwhenagivenpotential(voltage)existsbetweenitsleads.Theunitofcapacitance

isthefaradwhichisequaltoonecoulombpervolt.Thisisaverylargecapacitanceformost

practical purposes; typicalcapacitors have valueson theorder ofmicrofaradsor smaller.

Thebasicequationforcapacitanceis.

Where C is the capacitance in farads, V is the potential in volts, and Q is the charge

measuredincoulombs.Solvingthisequationforthepotentialgives:

Theimpedanceofacapacitoratanygivenangularfrequencyisgivenby:

wherejis ,istheangularfrequencyandCisthecapacitance.

Thechargeinthecapacitoratanygiventimeistheaccumulationofallofthecurrentwhich

hasflowedthroughthecapacitor.Therefore,thepotentialasafunctionoftimecanbewritten

as:

Wherei(t)isthecurrentflowingthroughthecapacitorasafunctionoftime.
http://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Faradshttp://en.wikipedia.org/wiki/Faradshttp://en.wikipedia.org/wiki/Capacitance


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TantalumcapacitorshavehighcapacitanceandlowESR,butlowoperatingvoltages.When

tantalumcapacitorsfail,ittendstobe"spectacular,"theyessentiallyblowup.

Thecapacitanceofaparallel-platecapacitorconstructedoftwoidenticalplaneelectrodesof

areaAatconstantspacingDisapproximatelyequaltothefollowing:

where C is the capacitance in farads, 0 is thePermittivity of Space, r is theDielectric

Constant,Aistheareaofthecapacitorplates,andDisthedistancebetweenthem.

Adielectricis thematerialbetweenthetwochargedobjects.Dielectricsareinsulators.They

impede the flowofcharge innormaloperation.Sometimes,whena too large voltagehas

been reached,chargestarts flowing.This iscalleddielectric breakdownand

Beginnerssometimes misunderstand this. Timing circuits do measure the

rate at which a capacitor charges, but they measure a threshold voltage instead

of allowing the voltage to build up until dielectric breakdown. (A device which

does function this way is a spark gap.)

No charge should ever flow from one plate to the other. Although a current does

flow through the capacitor, charges are not actually moving from one plate to

the other. As charges are added to one plate, their electric field displaces like

charges off of the other plate. This is called a displacement current.

CAPACITORMATERIALS

Capacitors can be made either polarized or non-polarized. A polarized capacitor

requires that the capacitor be hooked up such that the voltage is always biased

in one direction. Hooking a polarized capacitor backwards will result in the

capacitor exploding, sometimes releasing harmful fumes. Non-polarized

capacitors can be biased in either direction without harm to the capacitor.

Polarized and non-polarized capacitors have an upper limit of voltage, where the

material will break down and the capacitor will no longer function. This can also

cause fumes to be released depending on the type of material.

Different materials and their properties.These are normally low capacitance (between ~1pF to ~1F). Ceramic

capacitors have a very low inductance due to the shape. This means that the

capacitance value continues into extremely high frequencies, making them

perfect for RF applications. However, ceramic capacitors tend to vary their

capacitance with temperature.

C0G or NP0 - Typical 4.7 pF to 0.047 F, 5%. High tolerance and temperature

performance. Larger and more expensive.

X7R - Typical 3300 pF to 0.33 F, 10%. Good for non-critical coupling, timing

applications.
http://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikipedia.org/wiki/spark_gaphttp://en.wikipedia.org/wiki/spark_gaphttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilonhttp://en.wikibooks.org/wiki/Electronics/Voltage#Permittivity:_.26epsilon


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Z5U - Typical 0.01 F to 2.2 F, 20%. Good for bypass, coupling applications.

Low price and small size.

Slightly larger than ceramic, but still has small values (usually in

the picofarad range).

Polyester: from about 1 nF to 1 F

Polypropylene: low-loss, high voltage, resistant to breakdownThese are polarized capacitors that are still small enough to be

surface mount. Normally the dielectric breakdown voltage is rather low, so the

capacitors are not suitable for high voltage applicatons, typcially greater than 20

volts. Tantalum capacitors have a stable capacitance across varying

temperatures, and low ESR.

These are also polarized, are much larger than tantalums. The

dielectric strength is much higher in these, and so is the capacitance.

Capacitance values can range between 1F and 1mF (sometimes up into the

farad range). These are compact capacitors that are also very loss. They are

useful for smoothing power supplies because of the high capacitance.Air-gap

These capacitors are more compact than normal electrolytic capacitors,

giving capacitance values in the farad range, but normally have an extremely

low breakdown voltage.

Super capacitors 2500 F to 5000 F

CAPACITORJUNCTIONS

Capacitors in SeriesCapacitors in series are the same as increasing the distance between two

capacitor plates. As well, it should be noted that placing two 100 V capacitors in

series results in the same as having one capacitor with the total maximum

voltage of 200 V. This, however, is not recommended to be done in practice.

Especially with capacitors of different values. In a capacitor network in series,

.

In a series configuration, the capacitance of all the capacitors combined is the

sum of the reciprocals of the capacitance of all the capacito

Documents

Fundamentals of Electronics - Awais Yasin