模擬電子技術(shù)基礎(chǔ)(論文)

經(jīng)典word整理文檔，僅參考，雙擊此處可刪除頁眉頁腳。本資料屬于網(wǎng)絡(luò)整理，如有侵權(quán)，請聯(lián)系刪除，謝謝！摘要件，包括功率放大電路、運算放大電路、反饋放大電路、信號運算與處理電路、信目的。關(guān)鍵詞:模擬電子技術(shù)，二極管，信號發(fā)生器Electronictechnologyisthestudyofsimulationofthesimulationsignalprocessingcircuit.Analogcircuitasoneofelectricalengineeringanditsautomationprofessionalbackbonecourse,experiencedalonghair,nowhasbeenwidelyusedinourlife.Analogelectronictechnologyforsemiconductordiodes,semiconductortriodeandfieldeffecttubeasthekeyelectronics,includingpoweramplificationcircuit,operationalamplifiercircuit,feedbackamplificationcircuit,signaloperationandprocessingcircuit,signalcircuit,powersupplyvoltageregulatorcircuit,researchdirection,andcontinuouslyreformandinnovation,andappliedtotheproductionlife,greatlypromotedtheprogressofscienceandtechnology.Thisarticlesummarizesthedevelopmentandprospectofanalogelectronictechnology,andthenintotheanalogelectronictechnologyfoundationforeachchapterinexplanation,soastoachievetheaimofdeepunderstandmasteranalogelectronictechnology.Keywords:Analogelectronictechnologytriodeteachingsignalcircu緒論一、簡介模擬電子技術(shù)是電子技術(shù)的一個方面,他是一個非常美麗的地方,在這個領(lǐng)域,數(shù)學(xué)、物理、信息工程、電氣工程和自動化工程學(xué)科發(fā)現(xiàn)和諧集成點,其深刻的理論基礎(chǔ)和廣泛的實際應(yīng)用使它有一個強大而持久的生命力。因此,對于許多相關(guān)的科學(xué)。模擬電子技術(shù)是一個非常重要的基礎(chǔ)理論課程。一般來說,模擬電子技術(shù)是一個實用的,非常實用的課題,本文的主要目的是研究各種半導(dǎo)體器件的性能、電路及其應(yīng)用,模擬電子技術(shù),很多的概念,但在科學(xué)和工程專業(yè)知識的過程中學(xué)習(xí)。起著非常重要的作用,它不僅是為未來的課程奠定基礎(chǔ),為我們分析和解決問題的能力也是非常重要的。根據(jù)目前流行的說,就是使用一門外語(主要是英語)進行非語言學(xué)科的教學(xué),為學(xué)生創(chuàng)造一個密切接觸英語環(huán)境”。認(rèn)為,雙語教學(xué)被認(rèn)為是一種外語教學(xué)方法學(xué),雙語教學(xué)是它的目的,主要是指一個語言政策是一個多元文化的國家,而不僅僅是一種教學(xué)方式。雙語教學(xué)改革的實施不僅有利于培養(yǎng)素質(zhì)高、能力強,而且教師的英語水平的提高。作為一個重要的專業(yè)電工基礎(chǔ)課程,實施雙語教學(xué)是最好的選擇。模擬電子技術(shù)課程的雙語教學(xué)模式,經(jīng)過一系列的教學(xué)實踐和探索實踐證明效不僅讓學(xué)生根據(jù)其基本原理來解決遇到的問題的過程中學(xué)習(xí)和英語水平的提高,增強學(xué)生的學(xué)習(xí)興趣,讓他們覺得有用。模擬電子技術(shù)課程的教學(xué)目標(biāo)。模擬電子技術(shù)的特點是:線性和非線性的組合,直流和交流,結(jié)合電路和設(shè)備,系和緊密整合,全面介紹網(wǎng)絡(luò)圖論,通過計算機的影響,非線性電路與系統(tǒng)的研究方興未艾,集成電路和超大規(guī)模的快速發(fā)展的狀態(tài)將在很長一段時間對電路和系統(tǒng)科學(xué)的發(fā)展,在多通道設(shè)備,集成;在系統(tǒng)的分析方法,優(yōu)化集成;在系統(tǒng)擴展從線性到21世紀(jì),電子技術(shù)快速發(fā)展的時代,隨著技術(shù)的不斷改進,使設(shè)備規(guī)模繼續(xù)縮小,以不斷提高集成,降低功耗,旗艦性能得到了改進。I隨著時代的發(fā)展,將越來越多的雙語教學(xué)教師和所有年齡段的學(xué)生,一方面可以提高語言能力,另一個是與世界先進的電子技術(shù)知識的整合,擴大我們的視野,與英語的國際化和電子技術(shù)的快速發(fā)展,傳統(tǒng)的剛性的教學(xué)將逐步新穎便捷的多媒體技術(shù)來取代。多媒體課件的教學(xué)方法是一個基本出發(fā)點是基于文本、圖像、聲音、動畫和其他方式合作,刺激學(xué)生的感官,激發(fā)學(xué)生的興趣和嚴(yán)格的形式的多媒體課件和黑板,粉筆是沒有區(qū)別,獲得教學(xué)效果并不顯著。課件的制作適當(dāng)?shù)牟牧?適用于木材。多媒體課件可以充分發(fā)揮學(xué)生的潛能,強化教學(xué)效果,提高教學(xué)質(zhì)量為重心。但最終多媒體只是一種輔助教學(xué)手段,為了更好地利用先進的知識傳播工具。隨著當(dāng)今世界的發(fā)展，外語的應(yīng)用越來越廣泛，國內(nèi)外語環(huán)境較差。所以教育中國這個多元化國家，雙語教學(xué)不僅是一種教學(xué)模式，更是一種語言政策。模擬電合適的。II二、課題研究目的及意義習(xí)的過程中可以掌握兩種語言，提高對英語的理解，增強學(xué)習(xí)興趣，擴大學(xué)生的知識面。經(jīng)過一系列研究實踐和探索，雙語教學(xué)的效果理想，不僅專業(yè)上學(xué)以致用，所在了。三、國內(nèi)研究現(xiàn)狀和發(fā)展趨勢及綜述模擬電子技術(shù)的特點為：線性與非線性相結(jié)合，直流與交流相結(jié)合，電路與器件相結(jié)合，基本估算與物理概念相結(jié)合。目前，模擬電子技術(shù)的現(xiàn)狀可簡單地鬼難為：與系統(tǒng)理論緊密結(jié)合、全面引入網(wǎng)絡(luò)圖論、深受計算機的沖擊、非線性電路與最佳化、可集成化；在體系上從線性擴展到非線性、從無源擴展到有源、從單元件分立擴展到電路系統(tǒng)的集成。進入21實際，電子技術(shù)進入了飛速發(fā)展的時代，隨著工藝技術(shù)的不斷改進，使得器件的尺寸不斷縮小，從而集成度不斷提高，功耗降低，旗艦性能得到提高。1AnalogConcept..............................................................................................................11.1Elementandparameter.........................................................................................11.2Electroniccomponent...........................................................................................11.3Analogsignalanddigitalsingnal..........................................................................21.4TroubleshootingAnalogCircuits..........................................................................31.5Basictestinstrument.............................................................................................32DiodesandApplications.................................................................................................42.1TheAtomicStructureOfSemiconductors............................................................42.2ThePNJunction....................................................................................................62.3BiasingtheSemiconductorDiode........................................................................82.4Diodeclassification...............................................................................................93BipolarJunctionTransistors.........................................................................................103.1StructureofBipolarJunctionTransistors...........................................................103.2Transistoroperatingprinciple.............................................................................123.3CharacteristiccurveofBJT................................................................................143.4BJTBiasCircuits................................................................................................153.5Faultdiagnosisoftransistorbias........................................................................154FieldEffectTransistors.................................................................................................174.1StructureofFieldEffectTransistors...................................................................174.2JFETCharacteristics...........................................................................................184.3ThetransconductancecurveofJFET..................................................................194.4InputresistanceofJFET.....................................................................................204.5Differentialamplifier..........................................................................................215BasicOp-AmpCircuits.................................................................................................225.1Comparators........................................................................................................225.2TheEffectofNoiseonTheComparator............................................................245.3IntegratorsandDifferentiators...........................................................................25ConcludingRemarks........................................................................................................26Thank...............................................................................................................................27Reference.........................................................................................................................2811.1ElementandparameterAccordingtothetypesofsignalsthatweuse,wecantheelectroniccreditsintotwoparts:digitalelectronicsandanalogelectronics.Theanalogcircuitisusedforcontinuousvariation,whilethedigitalcircuitisusedtocorrespondtothediscretelevel.Analogelectronicsisthesignalprocessing,suchasamplification,differential,integral,andsoon.Anddigitalelectronics,includingarithmeticandlogicoperations,asistheuseofcomputersandcalculatorstocompletetheoperation.1.2ElectroniccomponentIntwentiethCentury,theelectronicsystemfromthesendertoChittagongvacuumtubes,transistorsandintegratedcircuits.Integratedcircuitisthefunctionofthecompletionoftheoriginal,itisdividedintodigitalintegratedcircuitwithanalogintegratedcircuit,oneistousetwodiscretevoltage,andtheotheristodealwiththecontinuouschangeoftheinputsignalwiththeoutputsignal.Inordinaryalgebra,linearequationscanbeexpressedinalinearrepresentationofvariables,andaregenerallywritteninaformula.Y=mx+bYsaidXisthedependentvariable,independentvariable,Mslope,BistheinterceptontheYaxis.Whentheinterceptiszero,istogothroughtheorigin,theBiszero,thentheformulaisY=mxLinearoriginalistheincreaseinthecurrentandthevoltageisproportionaltotheadded,butalsoinlinewiththeOhm'slaw.Formostelectroniccomponents,thecharacteristiccurveisthecurveofthecurrentversusvoltage(thegraphoftherelationshipbetweenthetwoelementsof1acomponentingeneral)isdefinedasthecharacteristiccurve.Ifthepowersupplyreverseconnection,thenthecircuitwillbewhatisnotthesame?Thistimewillproducemorereadings,willmakepeoplelookverymessy,pronetoerror.Theabovementionedcharacteristiccurveofresistanceisastraightorigin,andYaxiswithzerointercepttime.Theslopeofastraightlineisconstantandisequaltotheresistanceoftheelectricalconductivity,thatis,thereciprocaloftheslopeistheresistance.1.3AnalogsignalanddigitalsingnalInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,telecom,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtocompleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon.21.4TroubleshootingAnalogCircuitsInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,telecom,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtocompleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon.1.5BasictestinstrumentInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).3Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,telecom,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtocompleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon.22.1TheAtomicStructureOfSemiconductorsInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.4-1Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,telecom,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtocompleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.-25Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon-32.2ThePNJunctionAPNjunctionisadiode.Intheequilibriumstate,thereisnocurrentinthePNjunction.Themainuseofthesemiconductordiodeistheonewayelectricconductivity.6-4PNjunctionWhenapuresemiconductorisgenerallydopedntype,thegeneraldopingofPtype,theninbetweenthetworegionsontheformationofaPNnode.IntheNarea,therearemanyfreeelectronsandseveralholeswhicharethermallyproduced.Therearemanyholesinthepregion.Thefreeelectron.Pnstructureproducedbythehotelectronsisthebasicdiodeandthebasisoftheworkofallsolidstatecomponents.Diodeisacomponentthatonlyallowscurrenttoflowinonedirection.7-52.3BiasingtheSemiconductorDiodeThetermbiasinelectronicsreferstoafixedDCvoltagewhichisaddedtothesemiconductorelementtosetitsworkingconditions.ForwardbiasistheconditionthatallowsthecurrenttoflowthroughthePNjunction.ReversebiasisthebiasconditiontopreventthecurrentflowingthroughthePNjunction.Asshowninthefollowingfigure.TheleadoutofthePregioniscalledapositiveelectrodeorananode,andtheleadoutoftheNregioniscalledanegativeelectrodeoracathode3.4Diodeclassification8-62.4Diodeclassificationphotodiode:Thereversecurrentincreaseswiththeincreaseoftheintensityoflight.-79Whenaforwardcurrentflows,thelightofacertainwavelengthrangeissentout,andthecurrentlightemittingtubecanemitlightfrominfraredtovisiblelightband.-833.1StructureofBipolarJunctionTransistorsBipolartransistor,itisabbreviatedasBJT.Isconstructedfromthreedopedsemiconductorregions.Thesethreeregionsareknownastheemissionregion,thebaseregionandthecollectorregion(FigureA,b);-1thesethreeregionsareseparatedbytwopn.Weknowthatbipolartransistorsaredividedintotwotypes.OneofthetwoPnareasinthemiddleofaPNwithathinlayer,knownasNPNtypetransistor,thereisatwoPNarea,themiddleofathinlayerofPNclip,calledPNPtypetransistor.Thesetwokindsoftransistorsarewidelyusedbyus,buttheformerismorewidelyused.Somostofuslearnaboutit.-23.2TransistoroperatingprincipleInordertomakethetransistorworknormally,anexternalDCbiasvoltagemustbeprovidedontwoPnjunctionsinordertoestablishtheproperworkingconditions.NPNandPNPtubenormalbias,intwocases,thelaunchofthejunctionareforwardbias,theseasonisreversebias,knownaspositiveandnegativebias.-3Butinthetwocasethevoltagepolarityandthedirectionofthecurrentisjusttheopposite.FromemitteroutflowintothenarrowandlowdopingconcentrationofthebaseregionmostelectronicnocompositetwolittlecontinuestospreadtotheBCjunctiondepletionregion,onceintotheregiontheyinthereversebiasBCjunctionperiodwillbetheattractionbetweenpositiveandnegativeionsestablishedplantspull.Kirchhoff'scurrentlawpointsoutthatthetotalcurrentflowingintothenodemustbeequaltothetotalcurrentflowingoutofthenode.ApplyingthislawtotheNPNtubeandthePNPtubecanbeconcludedthattheemittercurrentIeisequaltothesetcurrentIcwhichisthesumofthebasecurrentIb.Theexpressionis:Ie=Ic+IbinwhichthecurrentrespectivelyshowstheNPNtubeandPNPtubesmallsignaltransistorofthetypicalcurrentvalue.3.3CharacteristiccurveofBJTTheBJTcharacteristiccurveisdividedintotheinputcharacteristiccurveandtheoutputcharacteristiccurve,andtheinputcharacteristiccurveisclosetothecommondiode.Thatistosayintheanalysisofbipolartransistorcircuit,ifthetransistoristurnedon,theemittervoltageatbothendsoftheregardedas0.7V.Ifthevoltageis0transistorturn-on,ifmuchlargerthan0.7thetransistoremitterjunctionisregardedasanopencircuit.InordertodrawtheoutputcharacteristiccurveoftheBJT,thebaselevelcurrentmustbeselectedandkeptconstant.Forexample,thecircuitusedtogenerateabaselevelcurrentintheroleofIcwiththeVcechangeofagroupofvoltamperecurve,thiscurveiscalledtheoutputcharacteristiccurve.-4-53.4BJTBiasCircuitsBiasistheadditionofproperDCvoltagetothetransistortoworkproperly.Itcanbeachievedthroughanyoneofseveralbasiccircuits.Theselectionofbiascircuitisveryrelatedtotheapplication.Inwhichthelinearamplifier,theinputsignalmustbeinthepositiveandnegativedirectionchange.Butthetransistorsworkinasingledirection.InordertoallowthetransistortoamplifytheACsignal,theACsignalisrequiredtobesuperimposedontheDCcapacityofthesetofgoodworkingpoints.ThebiascircuitsetstheDCtoallowtheACsignaltomoveinapositiveornegativedirectionwithoutmakingthetransistorinsaturationorcutoff3.5FaultdiagnosisoftransistorbiasAsthebiascircuitdiagnosisisusuallysimple,ordinarytransistorbiascircuitbiaspoorfaultbyresultedinthefollowingtwocasesa,thefirst:transistorinsaturationstatethesecond:transistorisoffstate.Inthebeginningofthediagnosticcircuit,thefirsttocheckthebase,collectorandemittervoltage.Itisverypracticaltoobservewhethertheyaresuitableornot.Wehavetokeepinmindthatthesevoltagesareusuallyassociatedwithsomeresistanceorthebetavalueofthetransistor,butthechangeisnotmorethan10%ofit,andifnormal,thecircuitcanworkproperly.Whenopencollectorresistance,duetolaunchresistancethereisnolongeracollectorcurrent,sothelaunchsomevoltagedrop:basevoltagechangewilldependsonthebias"width",thefixedbiaswillmakeanimpactonsmaller.ThistimeweneedtonoteisthatwhentheemitterReopencircuit,thebasevoltageisworkingnormallybutthetransistorismeasuredontheemittervoltageishigherthanthenormalvalue.Ofcourse,theremaybeotherproblems,butasafaultdiagnosismethod,shouldbefurtheranalysisoftheparametersofthemeasurement,inordertomoreaccuratelyidentifythefinalproblem.44.1StructureofFieldEffectTransistorsBeforewesaid,bipolartransistorisacurrentcontroldevice,whichusesthebasecurrenttocontrolthesizeofthecollectorcurrent.Thedifferenceisthatthefieldeffecttubeisakindofvoltagecontrolelement,thatis,thecurrentofthegatevoltagecontrolelement.Theycanbeusedinamplifyingcircuitandswitchingcircuit.-1Fieldeffecttubeis,referredtoasFET.Itisatypeofsemiconductordevice,anditsworkingprincipleiscompletelydifferentfromthepreviousBJT.Inthefieldeffecttube,theconductivepropertyofanarrowlongconductivechanneliscontrolledbyapowerplant,whichisformedbyaddingthethirdpolegrid.Itcanbedividedintotwoclasses:thefirstclass:thejunctiontypefieldeffecttube,whichischaracterizedbytheformationofaPNjunctionbetweenthegateandthechannelofthetube.Secondclass:thisclassiscalledmetaloxidesemiconductorfieldeffecttransistor,whichisusedtocontroltheelectricalconductivityofthechannel,theinsulationlayerisaverythinlayerofglass.-24.2JFETCharacteristicsThecharacteristiccurveofJFETcanbedividedintothreezones.Ohmaccess,constantcurrentarea,stoparea.Undernormalconditions,theyareallrunningintheohmicorconstantcurrentarea.Nditchjunctiontypefieldeffecttube,Nchannelatbothendsoftheleadoutoftwowires,theupperendiscalledthedrain,thelowerendiscalledthesource.Thischannelisaconductor,fortheNchannel,theelectronisthecarrierfluid,forthePchannel,theholeisthecarrier.Whenthereisnoexternalvoltage,thechanneldoesnotgenerateanydirectionofconductivecurrent.Bychangingthegatevoltage,thewidthofthechannelandtheresistanceofthechannelcanbecontrolled,therebycontrollingthesizeofthedraincurrentI.Whiteareasindicatethedepletionregiongeneratedbythereversebias.Thekeyideaisthatthechannelwidthiscontrolledbythegatevoltage.-34.3ThetransconductancecurveofJFETAneffectivewaytoobserveanycircuitistoshowtherelationshipbetweentheoutputandtheinput.Thischaracteristiciscalledthetransfercharacteristiccurve.BecausetheJFETiscontrolledbytheinputnegativevoltageandtheoutputisthedraincurrent,thecurveoftherotatingshaftisthecurveoftherelationshipbetweenIDandVGS.Bydividingtheoutputbytheinput,theresultistheunitoftheelectricalconductivity.Youcanthinkofitastheinputvoltageisconvertedintooutputcurrent;therefore,theprefix"cross"andinfrontofthe"conductance"producedthetransconductanceoftheword,thetransconductancecurveisJFETtransfercharacteristics.ThetransconductanceparametersinthetableG.Transconductancecurveisnotastraightline,thenonlinearrelationshipbetweentheoutputcurrentandinputvoltage,fieldeffecttransistorhasanonlineartransconductancecurves.Thisisveryimportant,whichindicatesthatthepipewilldistorttheinputsignal.Distortionisnotalwaysabadthing,suchasaradiomixeristheuseofthefieldeffectisbetterthanthecharacteristicsoftheBJTtocomplete.-44.4InputresistanceofJFETAsweknow,PNhasahighresistancewhenitisbiased.WhenJFETisworking,thePnjunctionbetweenthegatesourceisreversebiased.Therefore,thegateinputresistanceisveryhigh.ItisthisveryhighinputresistancethatbecomesthemaximumadvantageoftheBJToverthebaseJFET.JFETparametertableisoftenusedinagatesourcevoltagevaluecorrespondingtothegatereversecurrentIGSStoindicatethesizeoftheinputresistance,inputresistancecanbeobtainedbythefollowingequation.Twoverticallinesrepresenttheabsolutevalue.Intheparametertableabove,Vgsis15V,andIGSSisthemaximumvalueof-1..RIN===15Asseenfromtheresults,theinputresistanceofJFETisquitehigh.Butinpracticalapplications,thetotalinputresistanceshouldalsocontainaresistancethatisconnectedtothegate,sothetotalinputresistanceshouldbeintherangeof1~10M.4.5DifferentialamplifierDifferentialamplifierisanimportantamplifierwithmultipleapplications.Inparticular,theopampisaninputstage.Thenameofthedifferentialamplifierisderivedfromthedifferencebetweentheinputsignalwhichisaddedatthetwoinputterminals,thatis,thedifferencebetweenthetwosignals.Thesamesignalisnotamplifiedintheinput.Ithasanimportantcharacteristictoreducethecommonmodenoise.Unlikeotheramplifiers,thisamplifierhastwoinputsandtwooutputs.Thepipeswerecarefullymatchedandhadthesamecharacteristics.-5Inordertounderstanditsworkingprinciple,itisassumedthatthetwobasesaregrounded.Becausethepressuredropofthebaseemitterstructureisthediodevoltagedrop,theemittervoltageis-0.7V.Theemittercurrentonbothsidesisequal,equaltohalfofthecurrentinthecommonemitterresistance.Thecollectorcurrentofeachtubeisequaltothatoftheemittercurrent,whichisequaltothehalfoftheemitterresistancecurrent.Becausethecollectorcurrentisequal,thecollectorvoltageisequal.55.1ComparatorsTheopampisusedasanonlinearelementtocomparethemagnitudeofthetwovoltage.Inthisapplication,theoperationalamplifierisusingopenloop,aninputterminalisconnectedwithaninputvoltage,anotherinputendisconnectedwithareferencevoltage.Nowwetalkaboutseveralbasiccomparisoncircuits.-1Acomparatorisanopencircuitthatisusedtocomparetwoinputvoltagesandgeneratetwovaluescorrespondingtotheinputsize.Anapplicationofanoperationalcomparatoristomeasurewhethertheinputvoltageisbeyondacertainvalue.Duetooperationalamplifierhasaveryhighopenloopvoltagegain,sothedifferentialmodevoltagebetweenthetwoinputendsofthesmallwillsaturatetheamplifier,theoutputvoltagereachesthelimitvalue.Tested,whenthesinewaveisnegative,theoutputreachesthemaximumnegativevalue.Whenthesinewavepasseszero,theamplifierisforcedtoentertheoppositestate,andtheoutputbecomesthemaximumintegrity.Itcanbeseenthatthezerocrossingcomparatorcanbeusedasasquarewavecircuit,withasinewavegeneratedbyFangBo.Withtheabovezerocrossingcomparatorisnotthesame,non-zerocomparator.Afixedreferencevoltageonthereverseinputofthezerocrossingcomparatorcanbemodifiedintoapositiveandnegativevoltagecomparator.Itismorepracticalthanzero.Heusesavoltagedividertosetthereferencevoltageto:VREF=R2/R1+R2（+v）Amongthem,+Visthepositivesupplyvoltageamplifier,withzenerdiodesetreferencevoltage(VREF=VZ).AslongastheinputvoltageVinislessthanthereferencevoltage,theoutputwillremainthemaximumnegativevalue.Whentheinputvoltageexceedsthereferencevoltage,theoutputreachesthemaximumvalue.5.2TheEffectofNoiseonTheComparatorInmanypracticalsituations,noisecanbegeneratedontheinputline.Noisevoltagesuperimposedontheinputvoltage,willmakethecomparatorerrortochangetheoutputstate.Inordertounderstandtheeffectofnoiseonvoltage,weaddalowfrequencysinusoidalvoltagetotheinputofthezerocrossingcomparator.Observedwiththenoiseofthesinewavewiththecorrespondingoutputwaveform,canbeseen,whenthesinewavereached0,duetothepresenceofnoisesothatthetotalinputin0toseveralchanges,resultinginthewrongoutput.Mingledwiththenoiseoftheinputwillcausetheerroroftheoutputvoltage,becauseofthesameinputvoltagevalue,comparatorOPmayfromnegativeoutputstatevariabletothepositiveoutputstate,mayalsobecausedbyachangeintheoppositedirection,