電子信息類專業(yè)英語(李白萍).ppt

UnitNineMicroelectronics,PassageAIntroductiontoMicroelectronicsPassageBTheSimpleAtom,Conductors,InsulatorsandSemiconductorsPassageCDiodeandTransistor,PassageAIntroductiontoMicroelectronicsTheexploringofspaceandthedevelopmentofearthsatelliteshasincreasedtheimportanceofreducingthesizeandweightofelectroniccircuits.Also,eventhoughelectricityflowsquiterapidlyincomputersthetimedelayofthesignalintheinterconnectionsbetweenelectroniccomponentsisanimportantconsideration.Iftheinterconnectionsarereducedinsize,acomputercanperformoperationsatafasterspeed.Microelectronicsinvolvestheminiaturizationofregularelectroniccircuits.Acompleteelectroniccircuit,anoperationalamplifierforexample,whichcontainslargenumbersofindividualinterconnectedcomponents,suchasdiodesresistors,transistors,etc.maybeformedonaverysmallsinglesubstrate.Thecompleteminiaturizedcircuitisthencalledanintegratedcircuit.,Integratedcircuitsaresmall,light,rugged,andreliable.Theyrequirelesspowerandlowervoltagesthanequivalentmacroscopiccircuits;consequentlytheyoperateatlowertemperatures,andindividualcomponentsmaybeclosetogetherwithoutexceedingtheoperatingtemperaturelimit.RelativelylittlestraycapacitanceandshorttimedelaysareproducedbecauseoftheshortinterconnectionsbetweentheindividualcomponentsinIC.MaintenanceissimplifiedbecauseifacomponentoftheICfailsthecompleteICisusuallyreplaced.MassproductiontechniquesofplanetechnologyhavereducedthecostofmanyICsothattheyarealmostasinexpensiveasasingletransistor.EventuallymostconventionalcircuitswillbereplacedbyIC.,Therearetwotypesofbasicintegratedcircuit:monolithicintegratedcircuitandthethinorthickfilm.MonolithicICareconstructedinasinglesubstrateofsinglecrystalsemiconductor,usuallysilicon.ThinorthickfilmsICareformedonthesurfaceofaninsulatingmaterialsuchasglassoraceramic.HybridICcontainsmorethanasinglesubstrate,thetermhybridisalsoappliedtocombinationsofmonolithicandthinorthickfilmIC.,Integratedcircuitsarealsoclassifiedaccordingtotheirfunctions.DigitalorlogicalICareusedasswitches,theyareeitheronoroff.Incomputerstheonandoffstatescorrespondto0or1.OtherICiscalledlinearoranalogIC.1Integratedcircuitscanbeproducedusingeitherbipolaroruniquepolartransistors.Fieldeffecttransistors(FET)haveaadvantagesoverbipolartransistorsinmanycaseshowever.Theyarerelativelyhigh-impedancedevices,withacorrespondingreductionincurrentandpowerdissipation,andyethavehighpowergain.Thereductioninpowerdissipationisparticularlyimportantwhereacomplexcircuitistobeconcentratedintoasmallspace.Theproblemofextractingtheheatgeneratedinthecircuitmaythenbeadifficultone.2TheformofconstructionoftheFET,andparticularlytheMOSFET,alsolendsitselfwelltointegratedcircuitfabrication,andenablesresistorsandcapacitorstobeincludedreadilyintheintegratedcircuit.,Mostelectroniccircuitsarecomposedofactivedevices,e.g.transistorsanddiodes,togetherwithresistors(forbias,collectorload,impedancetransformation,etc.)andcapacitors(e.g.forcouplingacsignalswhileblockingdcsupplies).Eachoftheseelementscanbeproducedinaformsuitableforintegratedcircuitinclusionwithinlimitations,e.g.capacitancevaluesmustnotbetoolarge.Someelementsaredifficulttoproduceinasuitableform,e.g.inductiveelements,orlargecapacitors.Usuallysomealternativecircuitformcanbedevisedthatdispenseswiththerequirement.Otherwisetheymustbeincludedasanexternallumpedelement.,KEYWORDSmicroelectronic微電子amplifier放大器considerable相當?shù)?重要的substrate基質(zhì);底質(zhì)integrate綜合;使完全rug地毯;毯子reliable可靠maintenance維護;保持;維修film膠片;薄膜monolithic獨立的;完全統(tǒng)一的silicon硅hybrid混合物bipolar(電子)雙極的,FET(Fieldeffecttransistors)場效應(yīng)管impedance阻抗dissipation損耗extractive抽出;釋放出fabrication制造,裝配;捏造事實bias偏差;偏置capacitor電容inductive電感dispense分配lumpedelement集總元件transistor晶體管,NOTES1Integratedcircuitsarealsoclassifiedaccordingtotheirfunctions.DigitalorlogicalICareusedasswitches,theyareeitheronoroff.Incomputerstheonandoffstatescorrespondto0or1.OtherICiscalledlinearoranalogIC.也可根據(jù)其功能不同對集成電路進行分類。數(shù)字IC(也稱為邏輯IC)通常用作開關(guān)，表示接通或關(guān)斷。在計算中，接通和關(guān)斷狀態(tài)分別對應(yīng)“0”或“1”。另一種IC被稱為線性或模擬IC。eitheror表示兩者擇一，在文中譯為“要么要么”。,2Thereductioninpowerdissipationisparticularlyimportantwhereacomplexcircuitistobeconcentratedintoasmallspace.Theproblemofextractingtheheatgeneratedinthecircuitmaythenbeadifficultone.減小功率損耗是非常重要的，其方法是將一個復(fù)雜的電子線路集成為一小塊。這使得釋放電路工作時產(chǎn)生的熱量變成一個難題。Theproblemofmaythenbeadifficultone.文中的one表示強調(diào)這個問題，這種句式在科技英語中常被使用。extractingtheheat為釋放熱量的意思，extract的本意為“抽出，剝離”。在電子線路中，器件工作均會產(chǎn)生熱量，如果不能及時散熱，器件就不能穩(wěn)定工作。,PassageBTheSimpleAtom,Conductors,InsulatorsandSemiconductorsTheSimpleAtomThematerialsthatmakeupouruniversearecomposedofoveronehundredbasicandindividualtypesofmattercalledelements.Ninety-twooftheseelementsoccurnaturallyandtheremaindersareman-made.Eachelementhasaseparateidentifyofitsown,thatis,notwoelementshavethesamephysicalandchemicalproperties,norcananelementbesubdividedbyordinaryphysicalandchemicalmeansintosimpleelements.1Examplesofelementsaregold,mercuryandoxygen.,Elementscontainsmallerparticlescalledatoms.Inanyoneelementtheatomsareidenticalinstructure.Thedifferencebetweenanytwoelementssuchasgoldandmercuryisintheiratomicstructures.Theyhaveincommon,however,arelativelyheavyinnercorecalledanucleussurroundedbyoneormoreextremelylightparticlesofmattercalledelectrons.Thesimplestnucleusisamassofmatterabout2,000timestheweightofanelectron,andiscalledaproton.Morecomplexnucleicontainvariouscombinationsofprotonsandneutrons.Aneutronisaprotoncombinedwithanelectronandiselectronicallyneutral.,Electronswhirlaroundnucleiinmuchthesamemannerthattheplanetsofoursolarsystemtravelaroundthesun.Thedifferencebetweenanatomofoneelementandthatofanotherisinthenumberofprotonsandneutronscontainedinthenucleus.2Alltheelementsintheuniverse,andthereforeallmatter,iscomposedofprotons,neutrons,andelectrons.Theremustbeforceofattractionbetweenanucleusandtheelectronssurroundingit,otherwisetheelectronswouldflyoffintospace,inordertounderstanditsnature,wefindithelpfultocallthisforceacharge.Thechargeofthenucleusisdefinedaspositive,andtheoppositechargeoftheelectron,negative.Inviewofthefactthatoppositesattract,theforcebetweenthenucleusandtherotatingelectronarounditpreventstheelectronfromflyingoffintospace.,Anatom,whichhasallofitsorbital(rotating)electronshasasmanypositivechargesandthereforethenetchargeiszero.Whenanatomlosesanelectronthebalanceofchargeisdisturbedandtheatombecomespositivelycharged.Inthiscondition,theatomiscalledapositiveion.Incomparison,whenanatomacquiresanelectron,thebalanceofchargesisagaindisturbedandtheatombecomesnegativelycharged,suchanatomisreferredtoasanegativeion.,Conductors,InsulatorsandSemiconductorsAnysubstance,whichallowselectronstoflowfreelythroughitsstructureiscalledaconductor.Ingeneral,metalsaregoodconductors.Adefiniterelationshipexistsbetweengoodconductorsandtheiratomicstructures.Ingoodconductors,theouter-ringelectrons,whicharealsocalledvalenceelectrons,maybereleasedfromtheirorbitswithrelativeease.Atomwith1,2and3outerringelectrons,andthereforemostmetalsaregoodconductors.,Substance,whichpreventthepassageofelectronsthroughtheirstructuresarecalledinsulators.Insulatorshaveveryfeweasilyremovedelectronsintheirouterrings.Therearenoperfectinsulators:first,becauseofthepresenceofimpurities(foreignmaterials)whichcanneverbeentirelyremoved;andsecond,becauseevenasmallamountofheatwillcauseacertainnumberofvalenceelectronstobefreedfromtheiratoms.Insulatorsgenerallyhaveverystableatomicstructures,ofwhichthe4-electronouter-ringstructureistypical.Insuchastructure,thereisanabsenceofeasilyremovedelectrons.Exampleofgoodinsulatorsarecertaincompoundsofcarbon(abasicingredientofrubber)anddiamond,whichhasasimilaratomicstructure.,Semiconductorsareagroupofmaterials,whichconductelectronspoorlyandthereforecannotproperlybeclassifiedeitherasconductorsorinsulators.Generally,semiconductorsdifferfrominsulatorsinthattheirouter-ringelectronscandetachthemselvesfromtheirorbitsmoreeasilythanininsulators.Typicalsemiconductorsmaterialsaregermaniumandsilicon.Impuritiesmaybeaddedtopuresemiconductors.Thisresultsinsemiconductormaterials,whichmayeitherhaveanexcessoffreeelectronsoradeficiencyoforbitalelectrons.WhenanexcessofelectronsispresentwecallthematerialN-type;whenlackoforbitalelectronsoccurs,wecallthematerialP-type.BothN-typeandP-typesemiconductorsaremadebytreatedmaterials.suchasgermaniumandsiliconwithimpuritiessuchasarsenicandindium.3Theadditionofimpuritiestosemiconductorsiscalleddoping.,KEYWORDSnaturally自然的;天生具備identity標識;標志mercury汞,金屬的一種oxygen氧氣;氧元素nucleus原子核proton質(zhì)子neutrons中子force力量;力charge主管,看管;承載orbital眼眶;軌道positive正電negative負電,conductor導(dǎo)體semiconductor半導(dǎo)體insulator絕緣valence原子價impurity雜質(zhì)ion離子excess過剩germanium鍺deficiency缺乏arsenic砷indium銦dope摻雜whirl旋轉(zhuǎn),NOTES1Eachelementhasaseparateidentifyofitsown,thatis,notwoelementshavethesamephysicalandchemicalproperties,norcananelementbesubdividedbyordinaryphysicalandchemicalmeansintosimpleelements.每一種元素均有它自己的標識，也就是說，沒有兩個元素具有相同的物理和化學(xué)特性，一種元素也不能以普通的物理或化學(xué)方法被分為兩種簡單的元素。thatis是插入語。nor也不，提到句首使用時，句子要倒裝，表示強調(diào)。,2Electronswhirlaroundnucleiinmuchthesamemannerthattheplanetsofoursolarsystemtravelaroundthesun.Thedifferencebetweenanatomofoneelementandthatofanotherisinthenumberofprotonsandneutronscontainedinthenucleus.電子圍繞原子核旋轉(zhuǎn)，其方式類似于太陽系中行星圍繞太陽旋轉(zhuǎn)。一種元素的原子和另一種元素的原子的差別在于其原子核中的質(zhì)子數(shù)和中子數(shù)。inmuchthesamemannerthat中，inmanner意為“以的方式”，that是manner的定語從句。,3BothN-typeandP-typesemiconductorsaremadebytreatedmaterials,suchasgermaniumandsiliconwithimpuritiessuchasarsenicandindium.N型半導(dǎo)體和P型半導(dǎo)體是利用雜質(zhì)摻入純凈半導(dǎo)體而形成的，如將雜質(zhì)砷和銦摻入鍺和硅中。aremadebytreatedmaterials,treat原意為對待，treatedmaterials指前文將雜質(zhì)摻入純凈半導(dǎo)體的過程。,EXERCISEAfterreadingthepassageconcludethefollowingsentencestrueorfalse.1.Thematerialsthatmakeupouruniverseareatoms.()2.Generallywedistinguishtheelementsbytheiratomicstructures.Eachatomhasauniqueidentify.()3.Theatomisalwayscomposedofproton,neutronsandelectrons.()4.Whenthetemperatureishigh,anelectroncanattractamountheatandthenflyoffintospace.()5.Thesemiconductorcanpermitthecurrentthroughtheirbodyifsomeconditionissupplied.(),6.Ifyouputimpuritiesaddingtopuresemiconductors,thisresultsinsemiconductormaterials,whichonlyhaveanexcessoffreeelectrons.()7.Whenanexcessofelectronsispresent,wecallthematerialP-type;whenlackoforbitalelectronsoccurs,wecallthematerialN-type.()8.BothN-typeandP-typesemiconductorsaremadebytreatedmaterials.suchasgermaniumandsiliconwithimpuritiessuchasarsenicandindium.()9.Thecourseofadditionofimpuritiestosemiconductorsiscalleddoping.(),PassageCDiodeandTransistorTheBasicCrystalJunction(orDiode)Whenafreeelectronmeetsamovingholeinasemiconductormaterial,theelectronoccupiesthefreespaceandapositiveornegativechargenolongerexists;thatis,thechargeisneutralized.WhenaP-typeandaN-typecrystalarejoinedtomakeasinglesemiconductor,asshowninFigure9.1,currentwillflowinonedirectiononly.Asanexample,whenapowersourceisconnectedtothesemiconductorasshowninFigure9.2,thesemiconductorissaidtobeforwardbiased.,Figure9.1Thebasiccrystaljunction,Figure9.2Forwardbiasedconnectionin,Theholeswillberepelledtowardthejunctionbythepositivelychargedbatteryterminal,whereastheelectronsarepushedtowardthejunctionbythebatterysnegativeterminal.Atthejunction,theelectronscombinewiththehole.ElectronsenterthesemiconductorattheNterminaltoreplacetheelectronsthathavecombinedwiththeholes.Likewise,electronsleavethePterminalbyattractionofpositivevoltageandcreatenewholes.Thismovementofelectrons,fromthenegativevoltagesourcethroughthejunctionandfromthepositiveterminalofsemiconductortopositivevoltagesource,createsacurrentflow.Thuscurrentwillflowinasemiconductorwhenthesemiconductorisforwardbiased.,Whenthepolarityofthepowersourceisreversed,thesemiconductorissaidtobereversebiased.Theholesaremovedawayfromthejunctionbythenegativevoltage,whereastheelectronsaredrawfromthejunctionbythepositivevoltage.Thusthereislittleornocombiningofelectronsandholesatthejunction,andnocurrentwillflow.Inpracticalterms,therewillalwaysbeafewelectronsandholesnearthejunction,allowingaverysmallcurrenttopass.Thissmallcurrentisknownasleakagecurrentandisusuallyintheorderofafewmicroamperes(orpossiblypicoamperes).,WhenP-typeandN-typeregionsareformedinsamecrystal,thesemiconductorisknownasadiodeorrectifier.Theboundarybetweenthetworegionsistermedajunction.TheP-regionterminaliscalledtheanode,whereastheN-regionterminaliscalledthecathode.Usually,whensuchsemiconductorsareusedwithsignals,thesemiconductorsarecalleddiodesorsignaldiodes.Whenthedeviceisusedforconversionofalternatingcurrent(ac)todirectcurrent(dc),thesemiconductoriscalledarectifier.,BasicTwo-junctionorBipolarTransistorLikeadiode,atransistorcanbeusedtoprevent(orlimit)theflowofcurrentinonedirection,Theprimeuseforatransistor,however,istocontroltheamountofcurrentinacircuit.Thisisdonebyaddingasecondjunctiontothebasicdiodejunction,discussedintheabovesection.Forthisreason,suchtransistorsarecalledtwo-junctiontransistorsor,possibly,bipolartransistors.Theauthorpreferstheformertermbutrecognizesthatthelattertermisalsoincommonuse.,Therearetwopossiblearrangementsforthetwo-junctionintransistors:NPN,whereapositivesemiconductormaterial(holes)isplacedbetweentwonegativesemiconductormaterials(electrons),andPNP,wherethenegativematerial(electrons)isplacedbetweentwopositivematerials(holes).Witheitherjunctionarrangement,thebasictwo-junctiontransistorwillhavethreeelements.Theseelements,showinFigure9.3asanNPNarrangement,aretheemitter,whichemitselectrons;thecollector,whichcollectselectrons;andabase,whichcontrolstheflowofelectronsbycontrollingthechargeconcentrationatthetwo-junctionsoneithersideofthebase.,Figure9.3NPNandPNPtwo-junctiontransistorarrangements,Figure9.4showshowtwojunctiontransistoroperatesinitsbasiccircuit.Asshown,theemitter-basejunctionwillpasscurrenteasilybecausethejunctionisforwardbiased.Thecollector-basejunctionwillnotpasscurrent(exceptforasmallleakagecurrent)sincethejunctionisreversebiased.(Thetermbackisoftenusedinplaceofreversebias.),Figure9.4Basictwo-junctiontransistorbiascircuit,ItshouldbenotedthatthepolaritiesofbiasvoltageforanNPNtransistordifferfromthoseofaPNPtransistor;however,thenetresultsarethesame.Forexample,asshowninFigure9.4,theemitterisnegativewithrespecttothebase(NPN)toproduceaforwardbias.InFigure9.4,theemitterispositivewithrespecttobase(PNP)toproducethesameforwardbias.Similarly,thecollectorhasareversebiasforbothNPNandPNP,eventhoughthepolaritiesarerevered.Also,itshouldbenotedthatfornormaloperationanNPNhasitsbasebiasedpositivelywithrespecttoitsemitter.Conversely,aPNPbaseisnegativewithrespecttoitsemitter.,(a)Basictwo-junctiontransistoroperation.Duringnormaloperationofatwo-junctiontransistor,currentwillflowbetweenemitterandbaseandbetweenemitterandcollectorbutnotbetweencollectorandbase.Mostofthecurrentflowsbetweenemitterandcollector,becauseofthelargevoltagedifferenceexistingbetweentheseelements(thesumoftheemitter-basevoltageandthecollector-basevoltage).Thisproducesalargenumberofchargecarriers(positiveholesinaPNPornegativeelectronsinanNPN)thatdiffusethroughthisbaseregionwhenpassingfromemittertocollector(orviceversa).Fewofthesechargecarrierscombinewiththecharge(positiveinNPN,negativePNP)inthebase.,Morechargecarrierswillbepulledoutoftheemitterandmadeavailableforthecollectorifthebase-emittercurrentisincreased.ThiscanbeaccomplishedbymaskingthebasemorenegativeinaPNPtransistororbymakingthebasemorepositiveinanNPNtransistor.Ifthebase-emittervoltageisdecreased,lesschargecarrierswillbepulledformtheemitterandlessemitter-collectorcurrentwillflow.,Sinceverylittlevoltage(approximately0.2Vforgermaniumand0.5Vforsilicon)isrequiredtoproducealargecurrentflowintheemitter,inputpowertoatransistorislow.Mostoftheemittercurrentflowsinthecollectorcircuit,wherethevoltageismademuchlarger.Asaresult,arelativelylargeamountofpowercanbecontrolledinanexternalload(connectedinserieswiththecollectorcircuit)byasmallamountofpowerintheemittercircuit.Thepowergainofatransistor(theratioofoutputtopowerinput)canbe40,000orhigherinsomeapplications.,(b)BasicNPNtransistoroperation.InanNPNtransistor,thebase-emitterforwardbiascauseselectronsfromtheemittertomoveintothebase,asshowninFigure9.5.Electronsflowthroughthethinbaseintothecollectorregion,withonlyabout10%oftheelectronscombiningwiththebaseholes.Theremaining90%oftheelectronsareattractedtothepositivecollectorvoltage.Inmosttwo-junctiontransistor,thebaseiskeptaspossibletomaintainthebasecurrentataminimum.Thisisdonebyaddingaminimumofimpuritiestothebasematerial.Ineffect,basematerialisonlyslightlyN,incomparisontoemitterorcollectorthatareheavilydoped.,Figure9.5BasicNPNandPNPtwo-junctiontransistoroperation,(c)BasicPNPtransistoroperation.InaPNPtransistor,theforwardbiasbetweentheemitterandbasecausesholestoflowintohebase,asshowninFigure9.5.Thebaseisrelativelythin(andofhighpurity)sothatmostoftheholespassthroughintothecollectorregion.Theholesarethenattractedtothenegativecollectorvoltage,wheretheyareneutralizedbyelectronsformthepowersource.,(d)Basictwo-junctiontransistorsymbolsandreferencedesignations.Transistorsareindicatedbyappropriatesymbolsinschematicdiagrams.Inrarecase,transistorwillbeshownbyblockrepresentations.Figure9.6showsthebasictwo-junctiontransistorsymbolsandthecorrespondingblockrepresentationsforbothNPNandPNPtransistor.TheonlydifferencebetweenanNPNandaPNPtransistorsymbolisthearrowheadontheemitter.ThearrowheadpointsawayfromthebaseelementforanNPNandtowardthebaseforaPNP.Usually,thelettersc(collector),e(emitter),andb(base)showninFigure9.6areomittedformschematicdiagramssincetheelementscanbeidentifiedformthesymbol.,Figure9.6Basictwo-junctiontransistorsymbolsandreferencedesignations,TheappropriateletterportionofatransistorreferencedesignationisQ-TransistorsshouldbeidentifiedasQ1,Q2,Q101,Q301,etc.;however,transistorcanalsobeidentifiedbytheletterTorevenV,althoughthesedesignationsareobsolete.,