《電子信息專(zhuān)業(yè)英語(yǔ)》高職配套教學(xué)課件

English

forElectronics&Information專(zhuān)業(yè)英語(yǔ)特點(diǎn):specialityvocabulariessentences

目標(biāo):專(zhuān)業(yè)文獻(xiàn)資料的閱讀能力(forexample:articles,specifications,datasheet,userguide)公共英語(yǔ)KFCBMWVVTWCDMAWWWLANUnitOneBasicKnowledgeofElectronicsNewWordsandExpressionsresistance

[ri'zist?ns]

電阻resistor[ri'zist?] 電阻器capacitor[k?'p?sit?] 電容器capacitance[k?'p?sit?ns] 電容inductor[in'd?kt?] 電感器inductance[in'd?kt?ns] 電感unit 單位ubiquitous[ju:'bikwit?s]普遍存在的resistivity[ri:zis'tiv?ti,riz-]

電阻系數(shù)alloy['?l?i,?'l?i]

合金prefix[pri:'fiks,'pri:fiks]前綴voltage['v?ultid?] 電壓constant['k?nst?nt]

常數(shù)，常量criticalresistance 臨界電阻powerrating 額定功率enamelledcopperwire 漆包線(xiàn)ferritecores['ferait] 鐵氧體磁芯filtercircuits 濾波電路ferriterod 鐵磁棒AC 交流DC 直流charge[t?ɑ:d?] 電荷mold[m?uld]

模子，模型coil[k?il] 線(xiàn)圈frequency['frikw?nsi] 頻率Ohm'slaw歐姆定律electroniccircuits 電子電路timing

circuits 定時(shí)電路PassageA

Resistors,capacitorsandinductorsAresistorisatwo-terminalelectroniccomponentthatproducesavoltageacrossitsterminalsthatisproportionaltotheelectriccurrentthroughitinaccordancewithOhm'slaw:V=IR.Resistorsareelementsofelectricalnetworksandelectroniccircuitsandareubiquitousinmostelectronicequipment.Practicalresistorscanbemadeofvariouscompoundsandfilms,aswellasresistancewire(wiremadeofahigh-resistivityalloy,suchasnickel/chrome).Theprimarycharacteristicsofaresistoraretheresistance,thetolerance,maximumworkingvoltageandthepowerrating.Othercharacteristicsincludetemperaturecoefficient,noise,inductanceandcriticalresistance.Theohm(symbol:Ω)isaunitofelectricalresistance.Commonlyusedinelectricalandelectronicusagearethekilohmandmegohm.Capacitorsstoreelectriccharge.Theyareusedwithresistorsintiming

circuitsbecauseittakestimeforacapacitortofillwithcharge.TheyareusedtosmoothDCsuppliesbyactingasareservoirofcharge.TheyarealsousedinfiltercircuitsbecausecapacitorseasilypassAC(changing)signalsbuttheyblockDC(constant)signals.Capacitanceisameasureofacapacitor'sabilitytostorecharge.Alargercapacitancemeansthatmorechargecanbestored.Capacitanceismeasuredinfarads,symbolF.However1Fisverylarge,soprefixesareusedtoshowthesmallervalues.Threeprefixesareused,μ(micro),n(nano)andp(pico).Aninductorisformedbywindingwirearoundasuitablemoldtoformacoil.Itselectricalpropertyiscalledinductanceandtheunitforthisisthehenry,symbolH.1HisverylargesomH(milli-henry)andμH(micro-henry)areused,1000μH

=

1mHand1000mH

=

1H.Ironandferritecoresincreasetheinductance.InductorsaremainlyusedintunedcircuitsandtoblockhighfrequencyACsignals.TheypassDCeasily,butblockACsignals,thisistheoppositeofcapacitors.Inductorsarerarelyfoundinsimpleprojects,butoneexceptionisthetuningcoilofaradioreceiver.Thisisaninductorwhichyoumayhavetomakeyourselfbyneatlywindingenamelledcopperwirearoundaferriterod.Trytomatchthefollowingcolumns:1.two-terminalcomponent電子電路2.Ohm'slaw 額定功率3.electroniccircuits二端元件4.powerrating 歐姆定律5.criticalresistance濾波電路6.electriccharge 漆包線(xiàn)7.enamelledcopperwire電荷8.filtercircuits 臨界電阻PassageB

DirectandAlternatingCurrent

NewWordsandExpressionsbattery['b?t?ri] 電源applications應(yīng)用components器件、元件series['si?ri:z]

串聯(lián)parallel['p?r?lel]并聯(lián)apparatus[??p?'reit?s]

器件、儀器tandem['t?nd?m]串聯(lián)式、雙人的divide[di'vaid]

分離、隔開(kāi)recombining 合并、匯合opposite['?p?zit]

相反、不同reciprocal[ri'sipr?k?l]

倒數(shù)classification分類(lèi)、類(lèi)別direct 直流、直接alternating交流、交變current['k?r?nt]

電流abbreviation[?bri:vi'ei??n]縮寫(xiě)、簡(jiǎn)寫(xiě)polarity[p?u'l?r?ti]極性reverse[ri'v?:s]反轉(zhuǎn)、倒相constant['k?nst?nt] 恒定、不變、常量regulate['reɡjuleit]控制、調(diào)節(jié)pulsating 波動(dòng)的、脈動(dòng)的unfilter 未濾波的rectifier['rektifai?] 整流、整流器utility 應(yīng)用程序、功用periodically[?pi?ri'?dik?li] 周期性地cycle['saikl] 循環(huán)、周期frequency['frikw?nsi]頻率transmission[tr?nz'mi??n]

傳播、傳送vast[vɑ:st,v?st]

巨大的、廣大的majority[m?'d??riti]多數(shù)、大多數(shù)receiver接收器、接收機(jī)provided如果、假如transformer[tr?ns'f?:m?]變壓、變壓器PassageB

DirectandAlternatingCurrentCircuitsconsistingofjustonebatteryandoneloadresistanceareverysimpletoanalyze,buttheyarenotoftenfoundinpracticalapplications.Usually,wefindcircuitswheremorethantwocomponentsareconnectedtogether.Andtherearetwobasicwaysinwhichtoconnectmorethantwocircuitcomponents:seriesandparallel.Seriescircuitisacircuitinwhichtwoormorepiecesofapparatusareconnectedendtoendorintandemwherethecurrentisnotdividedatanypoint.Parallelcircuit,aclosedcircuitinwhichthecurrentdividesintotwoormorepathsbeforerecombiningtocompletethecircuit,istheoppositeofseriescircuit.Andweknowthatiftworesistorswereconnectedinseries.Togetthetotalresistanceoftworesistors,R1andR2,youaddthemtogether.Ontheotherhand,tofindtotalresistanceoftwoinparallelcircuits,youaddthereciprocalsoftheresistancesandtakethereciprocaloftheresult.Capacitorsandinductorinseriescircuitsorinparallelcircuitshasthesimilarcharacters.It’soneofthemainclassificationmethodsaboutcircuitinelectronics.Notbyconnectingmethodsofcomponentsincircuit,itiswellknownthatelectriccircuitisusuallydividedintotwoclasses:directcircuitandalternatingcircuit,bythesignalorcurrentflowingthroughdirectcurrent,abbreviation,dc,isacurrentthatalwaysflowsinthesamedirection(i.e.,thepolarityneverreverses).Thecurrentmightbeconstant,asfromabatteryoraregulatedpowersupply;itmightbepulsating,asfromanunfilteredrectifier.Andthesesystemsareusuallycalleddirectcurrentcircuit.ThefirstutilitysystemsinstalledbyEdisonuseddctechnology.NotlongafterEdisoninstalledhisdirectcurrentsystem,othersrealizedthattheuseofanalternatingcurrentsystemhadadvantagesoverthedc.Everytimeweturnonatelevisionset,aradio,oranyofaotherelectricalappliances,wearecallingonalternatingcurrentstoprovidethepowertooperatethem.But,whatisthealternatingcurrent?Differentfromdirectcurrentmovingthroughaconductororcircuitinonedirectiononly,alternatingcurrent,abbreviation,ac,isacurrentthatperiodicallyreversesitsdirectionofflow.Asfig.1-4showing,inonecycle,analternationstartsatzero,risestoamaximumpositivelevelat90degrees,returnstozeroat180degrees,risestoamaximumnegativelevelat270degrees,andagainreturnstozeroat360degrees.Thenumberofsuchcyclescompletedpersecondistermedtheacfrequency.IntheUnitedStatesandmanyotherareasoftheworld,thefrequencyis60hertzorcyclespersecond.Andinourcountrythecurrentusedforthetransmissionofelectricalenergyandtheoperationofcommonmachineshasafrequencyof50hertz.Aciswidelyusedfortheoperationofthevastmajorityofcircuits.,whichcanbetransmittedoverlongdistances,evenwithoutusingconnectingwiresbetweensourceandreceiver,providedthechangerateofcurrentisfastenough,transformedtovariousvoltagesandeasilytolargerorsmallervaluesusingadeviceknownasatransformer,butdccannot.However,inmanycircuitapplicationssuchasgeneralpurposelightingandheating,eitheracordccanbeused.Wecanconvertdctoacbyusingadc-acconverter,acircuitthatconvertsadcinputvoltageintoanacoutputvoltage,withorwithoutstep-uporstep-down,andactodcbyrectificationcircuitformedbythediode,resistorandcapacitor.Trytomatchthefollowingcolumns:1.step-up 負(fù)載2.step-down 直流電路3.dc-acconverter 交流電路4.regulatedpower整流電路5.loadresistance 直流-交流轉(zhuǎn)換器6.Seriescircuit 降壓7.Parallelcircuit 穩(wěn)壓電源8.directcircuit升壓9.alternatingcircuit并聯(lián)電路10.rectificationcircuit串聯(lián)電路Reading:IntegratedCircuitsIn1958,anextremelyimportantdevicewasinventedindependentlybyJackKilby,workingatTexasInstruments,andbyNoyceandMooreatFairchildSemiconductor:theintegratedcircuit(IC),whichcombinesBJTs,MOSFETs,resistors,andcapacitors,aswellastheirinterconnections,intoafunctionalcircuitonasinglechip.IntegratedCircuitsareusuallycalledICsorchips.Theyarecomplexcircuitswhicharecombinationofafewinterconnectedcircuitelementssuchastransistors,diodes,capacitorsandresistorsproducedinasinglemanufacturingprocessononeandthesamebearingstructure,calledthesubstrate,andintendedtoperformadefinitefunctioninvolvedinconvertinginformation.Intheearly1960s,ICscontainedperhaps100devices,andthesmallestfeatureswereabout25micrometers(μm).RealizingthatthecostofcomplexelectronicsystemscouldbereduceddramaticallybytheuseofmorecomplexICs,processengineershaveworkeddiligentlytoincreasethepracticaldimensionsofchipsandtoreducethesizesofthedevices.Today'smostadvancedICscontaininexcessof10milliondevicesandhavefeaturesassmallas0.25μm.(Ahumanhairisabout25μmindiameter.)Thetrendtowardsmallerdevicesisexpectedtocontinue.Inadditiontotheincreasednumberofdevices,thereductioninthesizeoffeaturesresultsinhigherperformance(i.e.,faster)digitalcircuits.Thus,wecananticipateevengreateradvancesinthefieldofelectronics.ThemanufacturingtechniquesusedforICscanbedividedintotwomaintypes:filmtechniqueandmonolithictechnique.AndICscanbeclassifiedbyfunctionintotwo:circuitstobeappliedindigitalsystemsandthosetobeappliedinlinearsystems.ThedigitalICsareemployedmostlyincomputers,electroniccounters,frequencysynthesizersanddigitalinstruments.AndtheanalogorlinearICsoperateoveracontinuousrange,andincludesuchdevicesasoperationalamplifiers.Theseadvanceswillresultfromteamworkbyphysicalelectronicsscientists,processengineers,circuitdesigners,andsystemsdesigners.Althoughthisbookprimarilyconsiderscircuitdesign,itprovidesusefulbackgroundinformationforallengineersintheelectronicsindustry.TheinventionofICisagreatrevolutionintheelectronicindustry.Sharpsize,weightreductionsarepossiblewiththesetechniques;andmoreimportantly,highreliability,excellentfunctionalperformance,lowcostandlowpowerdissipationcanbeachieved.ICsarewidelyusedintheelectronicindustry.Homework翻譯TheHistoryofElectricityAsearlyasthelatterpartof16thcentury,experimenterswereexploringthebehaviorofstaticelectricity.WilliamGilbertexperimentedwithelectricchargesanddischarges.In1750,BenjaminFranklinprovedthatlightningwaselectricalinnature.Neitherinvestigatordiscoveredanythingthatwassignificantfromthestandpointofelectricity.Discoveryofthepresenceofmagnetismincertainrocksproceededtheearliestknowledgeofelectricity.UnitTwoAnalogCircuitNewWordsandExpressionsdiode['dai?ud] 二極管nonlinear[n?n'lini?]非線(xiàn)性one-way 單向的valve[v?lv]

閥門(mén)semiconductor[?semik?n'd?kt?] 半導(dǎo)體schematic[ski:'m?tik] 原理圖symbol['simb?l] 圖表arrows 箭頭battery['b?t?ri]電源lamp[l?mp] 燈permit[p?'mit] 準(zhǔn)許prohibit[pr?u'hibit]

禁止polarity[p?u'l?r?ti]極性Conversely相反switch[swit?]

開(kāi)關(guān)oddly['?dli] 奇怪地invent 發(fā)明predominantly占主導(dǎo)地位的conventional

[k?n'ven??n?l]

習(xí)慣的、傳統(tǒng)的notation[n?u'tei??n]符號(hào)、標(biāo)記metallurgically[?mel?'l?:d?ikli]冶金silicon['silik?n]

硅n-type N型p-type P型juxtaposed[?d??kst?'p?uzd] 緊靠的ohmmeter['?um?mi:t?] 歐姆表qualitatively['kw?lit?tivli]

定性地purpose 目的expect 期望military['milit?ri]

軍用civilian[si'vilj?n] 民用peak[pi:k] 峰值clamper['kl?mp?] 鉗子rectification 整流photic['f?utik] 光decoration[?dek?'rei??n] 裝潢、裝飾TextDiodeAdiodeisanonlinearelectricaldeviceallowingcurrenttomovethroughitinonedirectionwithfargreatereasethanintheotherandusuallyactingasaone-wayvalveforcurrent.Themostcommonkindofdiodeinmoderncircuitdesignisthesemiconductordiode,althoughotherdiodetechnologiesexist.SemiconductordiodesaresymbolizedinschematicdiagramssuchasFig.2-1.InFig.2-1,arrowsindicatethedirectionofelectroncurrentflow.Whenplacedinasimplebattery-lampcircuit,thediodewilleitheralloworpreventcurrentthroughthelamp,dependingonthepolarityoftheappliedvoltage.(Fig.2-2)(a)Currentflowispermitted;thediodeisforwardbiased.(b)Currentflowisprohibited;thediodeisreversedbiased.Whenthepolarityofthebatteryissuchthatelectronsareallowedtoflowthroughthediode,thediodeissaidtobeforward-biased.Conversely,whenthebatteryis“backward”andthediodeblockscurrent,thediodeissaidtobereverse-biased.Adiodemaybethoughtofaslikeaswitch:“closed”whenforward-biasedand“open”whenreverse-biased.Oddlyenough,thedirectionofthediodesymbol's“arrowhead”pointsagainstthedirectionofelectronflow.Thisisbecausethediodesymbolwasinventedbyengineers,whopredominantlyuseconventionalflownotationintheirschematics,showingcurrentasaflowofchargefromthepositive(+)sideofthevoltagesourcetothenegative(-).Thisconventionholdstrueforallsemiconductorsymbolspossessing“arrowheads”.Thearrowpointsinthepermitteddirectionofconventionalflow,andagainstthepermitteddirectionofelectronflow.oddlyenough：稀奇的是holdstruefor：適用于Onewaytomakeasemiconductordiodeistometallurgicallycreateawaferofsiliconcontainingn-typematerialadjoiningp-typematerial.Inann-channelMOSFET,forexample,then-typedrainjuxtaposedtothep-typechannelregionformsadiode.Anohmmetermaybeusedtoqualitativelycheckdiodefunction.Thereshouldbelowresistancemeasuredonewayandveryhighresistancemeasuredtheotherway.Whenusinganohmmeterforthispurpose,besureyouknowwhichtestleadispositiveandwhichisnegative!Theactualpolaritymaynotfollowthecolorsoftheleadsasyoumightexpect,dependingontheparticulardesignofmeter.Thediodeispopularlyappliedinelectricequipmentwhetherformilitaryuseorcivilianuse.Forexample:peakdetector,clampercircuits,voltagemultipliersandrectificationwhichisthemostpopularapplicationofthediode.AndnowLED（LightEmittingDiode),atypeofdiodewhichcanbedirectlychangetheelectricsignalintothephoticsignal,ispopularlyusedforlighting,display,signalanddecorationinourdailylife.Exercises:Trytomatchthefollowingcolumns:1.MOSFET 正向偏置2.schematicdiagrams施加電壓3.forward-biased 高電阻4.reverse-biased電壓倍增器5.LED原理圖6.voltagemultipliers反向偏置7.highresistance 發(fā)光二極管8.appliedvoltage金屬氧化物半導(dǎo)體場(chǎng)效管

PassageBNewWordsandExpressionstransistor[tr?n'sist?] 三極管amplifier['?mplifai?]放大器response 反應(yīng)accuracy['?kjur?si]

精確，準(zhǔn)確digital 半導(dǎo)體analog 原理圖regulation[reɡju'lei??n] 圖表oscillators['?sileit?z]振蕩器package 包裝，封裝individually[indi'vidju?li]分別地，獨(dú)立地integrated集成的billion 十億，數(shù)以十億計(jì)的，大量fundamental[f?nd?'ment?l]基本的，必要的govern統(tǒng)治，控制cellular['seljul?]利用電臺(tái)網(wǎng)通訊的，蜂窩式無(wú)線(xiàn)通訊系統(tǒng)的categories['k?tiɡ?riz]類(lèi)別bipolar[bai'p?ul?]有兩極的，雙極的；兩極世界的junction

['d???k??n]

結(jié)點(diǎn)，會(huì)合點(diǎn)solid-state使用電晶體的，不用真空管的，researchers 研究人員laboratories[l?'b?r?t?riz]實(shí)驗(yàn)室consists 包含，包括sandwich['s?nwid?] 把……夾在……之間

emitter[i'mit?] 發(fā)射極collector 集電極base 基極element['elim?nt] 原理，特性conducting 傳導(dǎo)condition 狀態(tài)holes 空穴attract 吸引operation[?p?'rei??n]

工作，運(yùn)行opposite 相反的connecting 鏈接common 共有的，公共的electrode[i'lektr?ud] 電極configuration[k?nfiɡju'rei??n] 構(gòu)造，接法wired 連線(xiàn)，以線(xiàn)加強(qiáng)consume[k?n'sju:m]

消耗terminals 端子drain[drein]

漏極channel 溝道conductivity[k?nd?k'tiviti] 導(dǎo)電性potential[p?u'ten??l] 電壓，電勢(shì)PassageBTransistorThetransistorisanonlinearsemiconductordevicebeingsimilartothediode,commonlyusedasanamplifieroranelectricallycontrolledswitch.Becauseofitsfastresponseandaccuracy,thetransistormaybeusedinawidevarietyofdigitalandanalogfunctions,includingamplification,switching,voltageregulation,signalmodulation,andoscillators.Transistorsmaybepackagedindividuallyoraspartofanintegratedcircuit,whichmayholdabillionormoretransistorsinaverysmallarea.Sothetransistorisbecomingthefundamentalbuildingblockofthecircuitrythatgovernstheoperationofcomputers,cellularphones,andallothermodernelectronics.Therearetwomajortransistorcategories:ThebipolartransistorAlsocalled“thebipolarjunctiontransistor”(BJT)andthefieldeffecttransistor(FET).Thefirsttypeofsolid-stateelectronictransistorwasmadebyresearchersWilliamShockley,JohnBardeenandWalterBrattainatBellLaboratoriesinDecember1947.And“BipolarJunctionTransistor”wasinventedbyWilliamShocklyin1950whichisthecommonstanderofthecurrenttransistor.Thebipolarjunctiontransistorconsistsofthreeregionsofsemiconductormaterial.Onetypeiscalledan-p-ntransistor,inwhichtworegionsofn-typematerialsandwichaverythinlayerofp-typematerial.Thetwon-typematerialregionsofthen-p-ntransistorarecalledtheemitterandcollectorandthep-typematerialiscalledthebase.n-p-ntransistorsaresymbolizedinschematicdiagramssuchasFig2-3.Whenusedasanamplifyingelement,thebasetoemitterjunctionisina"forward-biased"(conducting)condition,andthebasetocollectorjunctionis"reverse-biased"ornon-conducting.Smallchangesinthebasetoemittercurrent(theinputsignal)causeeitherholes(forpnpdevices)orfreeelectrons(fornpn)toenterthebasefromtheemitter.Theattractingvoltageofthecollectorcausesthemajorityofthesechargestocrossintoandbecollectedbythecollector,resultinginamplification.Theonlyfunctionaldifferencebetweenap-n-ptransistorandann-p-ntransistoristheproperbiasing(polarity)ofthejunctionswhenoperating.Foranygivenstateofoperation,thecurrentdirectionsandvoltagepolaritiesforeachtypeoftransistorareexactlyoppositeeachother.Therearethreewaysofconnectingatransistor,dependingontheusetowhichitisbeingput.Thewaysareclassifiedbytheelectrodethatiscommontoboththeinputandtheoutput.Theyarecalled:(a)common-baseconfiguration(b)common-emitterconfiguration(c)common-collectorconfigurationAlthoughthefirsttransistorsandfirstsiliconchipsusedbipolartransistors,mostchipstodayareFET(fieldeffecttransistors)wiredasCMOSlogic,whichconsumelesspower.AFEThasthreeterminals，asource,adrainandagate.Thesemiconductorregionbetweensourceanddrainiscalledachannelanditsconductivityiscontrolledbythepotentialofthegateterminal.Exercises:Trytomatchthefollowingcolumns:1.signalmodulation 模擬電路2.analogfunctions信號(hào)調(diào)制3.cellularphones 雙極型晶體管4.BJT 共基極5.FET 手機(jī)、移動(dòng)電話(huà)6.crossinto場(chǎng)效應(yīng)晶體管7.properbiasing 共集電極8.common-base 穿過(guò)9.common-emitter正確偏置10.common-collector 共發(fā)射極ReadingAmplifierMuchasthegateabstractionformsthefoundationofmostofdigitalelectronics,theoperationalamplifierformsthebasisformuchofelectroniccircuitdesign.Theoperationalamplifierisarguablythemostusefulsingledeviceinanalogelectroniccircuitry.Withonlyahandfulofexternalcomponents,itcanbemadetoperformawidevarietyofanalogsignalprocessingtasks.Itisalsoquiteaffordable,mostgeneral-purposeamplifierssellingforunderadollarapiece.Moderndesignshavebeenengineeredwithdurabilityinmindaswell:severalop-ampsaremanufacturedthatcansustaindirectshort-circuitsontheiroutputswithoutdamage.Thenameoperationalamplifieroriginatesfromthebygonedaysoftheanalogcomputer(1940-1960),inwhichtheconstantsindifferentialequationswererepresentedbythegainsofamplifiers.Thustheseamplifiers,constructedfrombalancedpairsofspeciallymanufacturedvacuumtubes,hadtohavereliable,known,fixedgains.Becausetransistorsareinherentlymoretemperature-dependentthanvacuumtubes,itwasatfirstthoughtthatsatisfactorytransistorOpAmpscouldnotbebuilt.Butin1964,itwasdiscoveredthatbyfabricatingbalancedtransistorpairsclosetogetheronasinglesiliconchiptominimizethermalgradients,thetemperatureproblemscouldbeovercome.Andthuswereborninrapidsuccessionthe703,the709,andthentheubiquitous741.OpAmpsarerarelyusedforanalogcomputersnow,butinsteadhavebecomeuniversalbuildingblocksinallaspectsofanalogcircuitry.TheOpAmpisamultistagetwo-inputdifferentialamplifierthatisdesignedtobeanalmostidealcontroldevice,specifically,avoltage-controlledvoltagesource.AnabstractrepresentationoftheoperationalamplifiershowninFig2-4suggestsitisafour-portdevice.Thefourportsareaninputport,anoutputport,andapairofpowerports.A+VS-voltage(forexample,15volts)isappliedatthepluspowerportanda?VS-voltage(forexample,?15volts)isappliedattheminuspowerport.Aninputvoltage(thecontrol)appliedacrossthenon-invertingandinvertinginputterminalsoftheOpAmpisamplifiedbyalargeamountandappearsattheoutputport.Intheoperationalamplifierabstraction,theinputimpedanceacrosstheinputportisinfinity,andtheoutputimpedanceiszero.Thegain,orthefactorbywhichtheinputvoltageisamplified,isalsoinfinity.ThesymbolandstandardlabelingfortheoperationalamplifierareshowninFig2-4(a).Thetworequiredexternalpowersupplieshavebeenexplicitlyshowninthediagram,althoughshowingthemisnottheusualpractice.Allfivecurrentshavebeenlabeled,inadditiontoappropriatenodevoltages,referredtotheindicatedcommongroundterminal.Inthisprimitivecircuit,thevoltageviisusedtocontroltheoutputvoltagevo.Letusexaminethiscontrolfunctionindetailtofindoutboththeextentofthecontrol,andthecostofthecontrol;thatis,howmuchpowermustbeappliedfromsourcevitocontrolagivenamountofpoweratthevoterminal.Toaddressthefirstproblem,wesetupthecircuitexactlyasinFig2-5(a),andmeasuretheoutputvoltagevo,bothasafunctionoftimeandasafunctionofvi,assumingviissomelow-frequencysinusoid.TheresultsareshowninFig2-5(b)and2-5(c).Notethedifferenceinscaleofthevoltageaxes,indicatingthattheoutputvoltageisperhaps300,000timesaslargeastheinputvoltage.Theplotofvoversusvishowsaregionaroundtheoriginwherevoisfairlylinearlyrelatedtovi,butmuchbeyondthisrangethecontrolbecomesineffective,andvostaysatafixedvoltage,orsaturates,atroughlyeither+12voltsor?12volts,dependingonthepolarityofvi.ThecurveswillalsodifferfordifferentsamplesofthesameOpAmptype.Differentdevicesofthesametypemighthavedifferentcharacteristics.Thecharacteristicsmightalsodependontemperature.Onekeytotheusefulnessoftheselittlecircuitsisintheengineeringprincipleoffeedback,particularlynegativefeedback,inwhichaportionoftheoutputsignaloftheOpAmpisfedbacktothev?