模擬電子技術(shù)基礎(chǔ)(論文)

..摘要模擬電子技術(shù)是一門研究對仿真信號處理的模擬電路學(xué)科。模擬電路作為電氣工程及其自動化專業(yè)主干課程之一，經(jīng)歷了長足的發(fā)，目前已經(jīng)被廣泛應(yīng)用在我們的生活中。模擬電子技術(shù)以半導(dǎo)體二極管、半導(dǎo)體三極管和場效應(yīng)管為關(guān)鍵電子器件，包括功率放大電路、運算放大電路、反應(yīng)放大電路、信號運算與處理電路、信號產(chǎn)生電路、電源穩(wěn)壓電路等研究方向，不斷的改革創(chuàng)新，并應(yīng)用到生產(chǎn)生活當(dāng)中，極大的推動了科技的進步。本文概述了模擬電子技術(shù)的開展過程及其前景，接著對模擬電子技術(shù)根底每章節(jié)進展雙語詳解，從而到達深層次理解掌握模擬電子技術(shù)的目的。關(guān)鍵詞:模擬電子技術(shù)，二極管，信號發(fā)生器..ABSTRACTElectronic

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technology.Keywords:Analogelectronictechnology;triode;teaching;signalcircu..緒論簡介模擬電子技術(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,其深刻的理論根底和廣泛的實際應(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)是一個非常重要的根底理論課程。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根底,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)進展非語言學(xué)科的教學(xué),為學(xué)生創(chuàng)造一個密切接觸英語環(huán)境〞。認為,雙語教學(xué)被認為是一種外語教學(xué)方法不夠全面。在當(dāng)今世界,有很多多元文化國家根據(jù)實際情況,在一些學(xué)校實施雙語教學(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)電工根底課程,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果是比擬理想的,可以更好地擴大學(xué)生的知識,提高學(xué)習(xí)能力。根據(jù)雙語教學(xué)的模式,不僅讓學(xué)生根據(jù)其根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,根本的估計和物理概念的組合。目前,模擬電子技術(shù)的現(xiàn)狀可以簡單地鬼說:理論體系和嚴(yán)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)模的快速開展的狀態(tài)將在很長一段時間對電路和系統(tǒng)科學(xué)的開展,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)擴展從線性到非線性,從被動到主動,從單一元素離散擴展到集成電路系統(tǒng)。進入21世紀(jì),電子技術(shù)快速開展的時代,隨著技術(shù)的不斷改良,使設(shè)備規(guī)模繼續(xù)縮小,以不斷提高集成,降低功耗,旗艦性能得到了改良。隨著時代的開展,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)的快速開展,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)方法是一個根本出發(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。課題來源隨著當(dāng)今世界的開展，外語的應(yīng)用越來越廣泛，國外語環(huán)境較差。所以教育需要創(chuàng)新，為此我們學(xué)校領(lǐng)導(dǎo)及教師讓我們以雙語課件為主題寫一篇論文。雙語教學(xué)不僅可以讓學(xué)生與英語有親密的環(huán)境，也能讓教師的整體素質(zhì)能力得到提高。在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。模擬電子技術(shù)作為一門電類相關(guān)專業(yè)的重要專業(yè)根底教程之一，實施雙語教學(xué)模式是非常適宜的。課題研究目的及意義對于這次模擬電子技術(shù)根底使用雙語教學(xué)模式，我們主要目的是能讓學(xué)生在學(xué)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，外語能力也得到提高，學(xué)習(xí)也更加有興趣了。這就是模擬電子技術(shù)雙語教學(xué)的目的所在了。國研究現(xiàn)狀和開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，根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)理論嚴(yán)密結(jié)合、全面引入網(wǎng)絡(luò)圖論、深受計算機的沖擊、非線性電路與系統(tǒng)的研究方興未艾、集成電路的出現(xiàn)并向超大規(guī)模迅速開展的狀況將在相當(dāng)長時間左右電路與系統(tǒng)學(xué)科的開展；在器件上多段話、集成化；在分析方法上系統(tǒng)化、最正確化、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)進入了飛速開展的時代，隨著工藝技術(shù)的不斷改良，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。..Catalog1AnalogConcept 21.1Elementandparameter 21.2Electronicponent 21.3Analogsignalanddigitalsingnal 21.4TroubleshootingAnalogCircuits 21.5Basictestinstrument 22DiodesandApplications 22.1TheAtomicStructureOfSemiconductors 22.2ThePNJunction 22.3BiasingtheSemiconductorDiode 22.4Diodeclassification 23BipolarJunctionTransistors 23.1StructureofBipolarJunctionTransistors 23.2Transistoroperatingprinciple 23.3CharacteristiccurveofBJT 23.4BJTBiasCircuits 23.5Faultdiagnosisoftransistorbias 24FieldEffectTransistors 24.1StructureofFieldEffectTransistors 24.2JFETCharacteristics 24.3ThetransconductancecurveofJFET 24.4InputresistanceofJFET 24.5Differentialamplifier 25BasicOp-AmpCircuits 25.1parators 25.2TheEffectofNoiseonTheparator 25.3IntegratorsandDifferentiators 2ConcludingRemarks 2..Thank 2Reference 2..AnalogConceptElementandparameterAccordingtothetypesofsignalsthatweuse,wecantheelectroniccreditsintotwoparts:digitalelectronicsandanalogelectronics.Theanalogcircuitisusedforcontinuousvariation,whilethedigitalcircuitisusedtocorrespondtothediscretelevel.Analogelectronicsisthesignalprocessing,suchasamplification,differential,integral,andsoon.Anddigitalelectronics,includingarithmeticandlogicoperations,asistheuseofputersandcalculatorstopletetheoperation.ElectronicponentIntwentiethCentury,theelectronicsystemfromthesendertoChittagongvacuumtubes,transistorsandintegratedcircuits.Integratedcircuitisthefunctionofthepletionoftheoriginal,itisdividedintodigitalintegratedcircuitwithanalogintegratedcircuit,oneistousetwodiscretevoltage,andtheotheristodealwiththecontinuouschangeoftheinputsignalwiththeoutputsignal.Inordinaryalgebra,linearequationscanbeexpressedinalinearrepresentationofvariables,andaregenerallywritteninaformula.Y=mx+bYsaidXisthedependentvariable,independentvariable,Mslope,BistheinterceptontheYaxis.Whentheinterceptiszero,istogothroughtheorigin,theBiszero,thentheformulaisY=mxLinearoriginalistheincreaseinthecurrentandthevoltageisproportionaltotheadded,butalsoinlinewiththeOhm'slaw.Formostelectronicponents,thecharacteristiccurveisthecurveofthecurrentversusvoltage(thegraphoftherelationshipbetweenthetwoelementsofaponentingeneral)isdefinedasthecharacteristiccurve.Ifthepowersupplyreverseconnection,thenthecircuitwillbewhatisnotthesame"Thistimewillproducemorereadings,willmakepeoplelookverymessy,pronetoerror.Theabovementionedcharacteristiccurveofresistanceisastraightorigin,andYaxiswithzerointercepttime.Theslopeofastraightlineisconstantandisequaltotheresistanceoftheelectricalconductivity,thatis,thereciprocaloftheslopeistheresistance.AnalogsignalanddigitalsingnalInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,tele,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtopleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon.TroubleshootingAnalogCircuitsInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,tele,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtopleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon.BasictestinstrumentInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,tele,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtopleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenon.DiodesandApplicationsTheAtomicStructureOfSemiconductorsInanalogelectronics,asignalisavoltageorcurrentthatcontainsinformation.Andelectronicsystemsignalisoftenusedinawaytodealwithorcantransformthewaveformaswellasthroughtheamplificationtoimproveenergy.Thiswaycanbecarriedoutinacontinuousmanner.Weknowthatthesignalisdividedintocontinuousordiscretetype,inwhichthecontinuoussignaltransformationisflatandslow,whichisnotinterrupted.Butdiscretesignalscanonlytakeonepart(forexample,someofthem).Continuousanddiscretecanbeusedfortheamplitudeofthesignalcanalsobeusedfortime.Ontheotherhand,anothertypeofencoderonlysomedatayouchoosetostepin.viewSTYLEREF1\s2-SEQ圖\*ARABIC\s11Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,tele,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtopleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.viewSTYLEREF1\s2-SEQ圖\*ARABIC\s12Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenonviewSTYLEREF1\s2-SEQ圖\*ARABIC\s13ThePNJunctionAPNjunctionisadiode.Intheequilibriumstate,thereisnocurrentinthePNjunction.Themainuseofthesemiconductordiodeistheonewayelectricconductivity.viewSTYLEREF1\s2-SEQ圖\*ARABIC\s14PNjunctionWhenapuresemiconductorisgenerallydopedntype,thegeneraldopingofPtype,theninbetweenthetworegionsontheformationofaPNnode.IntheNarea,therearemanyfreeelectronsandseveralholeswhicharethermallyproduced.Therearemanyholesinthepregion.Thefreeelectron.Pnstructureproducedbythehotelectronsisthebasicdiodeandthebasisoftheworkofallsolidstateponents.Diodeisaponentthatonlyallowscurrenttoflowinonedirection.viewSTYLEREF1\s2-SEQ圖\*ARABIC\s15BiasingtheSemiconductorDiodeThetermbiasinelectronicsreferstoafixedDCvoltagewhichisaddedtothesemiconductorelementtosetitsworkingconditions.ForwardbiasistheconditionthatallowsthecurrenttoflowthroughthePNjunction.ReversebiasisthebiasconditiontopreventthecurrentflowingthroughthePNjunction.Asshowninthefollowingfigure.TheleadoutofthePregioniscalledapositiveelectrodeorananode,andtheleadoutoftheNregioniscalledanegativeelectrodeoracathode3.4 DiodeclassificationviewSTYLEREF1\s2-SEQ圖\*ARABIC\s16Diodeclassificationphotodiode:Thereversecurrentincreaseswiththeincreaseoftheintensityoflight.viewSTYLEREF1\s2-SEQ圖\*ARABIC\s17Whenaforwardcurrentflows,thelightofacertainwavelengthrangeissentout,andthecurrentlightemittingtubecanemitlightfrominfraredtovisiblelightband.viewSTYLEREF1\s2-SEQ圖\*ARABIC\s18BipolarJunctionTransistorsStructureofBipolarJunctionTransistorsBipolartransistor,itisabbreviatedasBJT.Isconstructedfromthreedopedsemiconductorregions.Thesethreeregionsareknownastheemissionregion,thebaseregionandthecollectorregion(FigureA,b);viewSTYLEREF1\s3-SEQ圖\*ARABIC\s11thesethreeregionsareseparatedbytwopn.Weknowthatbipolartransistorsaredividedintotwotypes.OneofthetwoPnareasinthemiddleofaPNwithathinlayer,knownasNPNtypetransistor,thereisatwoPNarea,themiddleofathinlayerofPNclip,calledPNPtypetransistor.Thesetwokindsoftransistorsarewidelyusedbyus,buttheformerismorewidelyused.Somostofuslearnaboutit.viewSTYLEREF1\s3-SEQ圖\*ARABIC\s12TransistoroperatingprincipleInordertomakethetransistorworknormally,anexternalDCbiasvoltagemustbeprovidedontwoPnjunctionsinordertoestablishtheproperworkingconditions.NPNandPNPtubenormalbias,intwocases,thelaunchofthejunctionareforwardbias,theseasonisreversebias,knownaspositiveandnegativebias.viewSTYLEREF1\s3-SEQ圖\*ARABIC\s13Butinthetwocasethevoltagepolarityandthedirectionofthecurrentisjusttheopposite.FromemitteroutflowintothenarrowandlowdopingconcentrationofthebaseregionmostelectronicnopositetwolittlecontinuestospreadtotheBCjunctiondepletionregion,onceintotheregiontheyinthereversebiasBCjunctionperiodwillbetheattractionbetweenpositiveandnegativeionsestablishedplantspull.Kirchhoff'scurrentlawpointsoutthatthetotalcurrentflowingintothenodemustbeequaltothetotalcurrentflowingoutofthenode.ApplyingthislawtotheNPNtubeandthePNPtubecanbeconcludedthattheemittercurrentIeisequaltothesetcurrentIcwhichisthesumofthebasecurrentIb.Theexpressionis:Ie=Ic+IbinwhichthecurrentrespectivelyshowstheNPNtubeandPNPtubesmallsignaltransistorofthetypicalcurrentvalue.CharacteristiccurveofBJTTheBJTcharacteristiccurveisdividedintotheinputcharacteristiccurveandtheoutputcharacteristiccurve,andtheinputcharacteristiccurveisclosetothemondiode.Thatistosayintheanalysisofbipolartransistorcircuit,ifthetransistoristurnedon,theemittervoltageatbothendsoftheregardedas0.7V.Ifthevoltageis0transistorturn-on,ifmuchlargerthan0.7thetransistoremitterjunctionisregardedasanopencircuit.InordertodrawtheoutputcharacteristiccurveoftheBJT,thebaselevelcurrentmustbeselectedandkeptconstant.Forexample,thecircuitusedtogenerateabaselevelcurrentintheroleofIcwiththeVcechangeofagroupofvoltamperecurve,thiscurveiscalledtheoutputcharacteristiccurve.viewSTYLEREF1\s3-SEQ圖\*ARABIC\s14viewSTYLEREF1\s3-SEQ圖\*ARABIC\s15BJTBiasCircuitsBiasistheadditionofproperDCvoltagetothetransistortoworkproperly.Itcanbeachievedthroughanyoneofseveralbasiccircuits.Theselectionofbiascircuitisveryrelatedtotheapplication.Inwhichthelinearamplifier,theinputsignalmustbeinthepositiveandnegativedirectionchange.Butthetransistorsworkinasingledirection.InordertoallowthetransistortoamplifytheACsignal,theACsignalisrequiredtobesuperimposedontheDCcapacityofthesetofgoodworkingpoints.ThebiascircuitsetstheDCtoallowtheACsignaltomoveinapositiveornegativedirectionwithoutmakingthetransistorinsaturationorcutoffFaultdiagnosisoftransistorbiasAsthebiascircuitdiagnosisisusuallysimple,ordinarytransistorbiascircuitbiaspoorfaultbyresultedinthefollowingtwocasesa,thefirst:transistorinsaturationstatethesecond:transistorisoffstate.Inthebeginningofthediagnosticcircuit,thefirsttocheckthebase,collectorandemittervoltage.Itisverypracticaltoobservewhethertheyaresuitableornot.Wehavetokeepinmindthatthesevoltagesareusuallyassociatedwithsomeresistanceorthebetavalueofthetransistor,butthechangeisnotmorethan10%ofit,andifthesearenormal,thecircuitcanworkproperly.Whenopencollectorresistance,duetolaunchresistancethereisnolongeracollectorcurrent,sothelaunchsomevoltagedrop:basevoltagechangewilldependsonthebias"width",thefixedbiaswillmakeanimpactonsmaller.ThistimeweneedtonoteisthatwhentheemitterReopencircuit,thebasevoltageisworkingnormallybutthetransistorismeasuredontheemittervoltageishigherthanthenormalvalue.Ofcourse,theremaybeotherproblems,butasafaultdiagnosismethod,shouldbefurtheranalysisoftheparametersofthemeasurement,inordertomoreaccuratelyidentifythefinalproblem.

FieldEffectTransistorsStructureofFieldEffectTransistorsBeforewesaid,bipolartransistorisacurrentcontroldevice,whichusesthebasecurrenttocontrolthesizeofthecollectorcurrent.Thedifferenceisthatthefieldeffecttubeisakindofvoltagecontrolelement,thatis,thecurrentofthegatevoltagecontrolelement.Theycanbeusedinamplifyingcircuitandswitchingcircuit.viewSTYLEREF1\s4-SEQ圖\*ARABIC\s11Fieldeffecttubeis,referredtoasFET.Itisatypeofsemiconductordevice,anditsworkingprincipleispletelydifferentfromthepreviousBJT.Inthefieldeffecttube,theconductivepropertyofanarrowlongconductivechanneliscontrolledbyapowerplant,whichisformedbyaddingthethirdpolegrid.Itcanbedividedintotwoclasses:thefirstclass:thejunctiontypefieldeffecttube,whichischaracterizedbytheformationofaPNjunctionbetweenthegateandthechannelofthetube.Secondclass:thisclassiscalledmetaloxidesemiconductorfieldeffecttransistor,whichisusedtocontroltheelectricalconductivityofthechannel,theinsulationlayerisaverythinlayerofglass.viewSTYLEREF1\s4-SEQ圖\*ARABIC\s12JFETCharacteristicsThecharacteristiccurveofJFETcanbedividedintothreezones.Ohmaccess,constantcurrentarea,stoparea.Undernormalconditions,theyareallrunningintheohmicorconstantcurrentarea.Nditchjunctiontypefieldeffecttube,Nchannelatbothendsoftheleadoutoftwowires,theupperendiscalledthedrain,thelowerendiscalledthesource.Thischannelisaconductor,fortheNchannel,theelectronisthecarrierfluid,forthePchannel,theholeisthecarrier.Whenthereisnoexternalvoltage,thechanneldoesnotgenerateanydirectionofconductivecurrent.Bychangingthegatevoltage,thewidthofthechannelandtheresistanceofthechannelcanbecontrolled,therebycontrollingthesizeofthedraincurrentI.Whiteareasindicatethedepletionregiongeneratedbythereversebias.Thekeyideaisthatthechannelwidthiscontrolledbythegatevoltage.viewSTYLEREF1\s4-SEQ圖\*ARABIC\s13ThetransconductancecurveofJFETAneffectivewaytoobserveanycircuitistoshowtherelationshipbetweentheoutputandtheinput.Thischaracteristiciscalledthetransfercharacteristiccurve.BecausetheJFETiscontrolledbytheinputnegativevoltageandtheoutputisthedraincurrent,thecurveoftherotatingshaftisthecurveoftherelationshipbetweenIDandVGS.Bydividingtheoutputbytheinput,theresultistheunitoftheelectricalconductivity.Youcanthinkofitastheinputvoltageisconvertedintooutputcurrent;therefore,theprefix"cross"andinfrontofthe"conductance"producedthetransconductanceoftheword,thetransconductancecurveisJFETtransfercharacteristics.ThetransconductanceparametersinthetableG.Transconductancecurveisnotastraightline,thenonlinearrelationshipbetweentheoutputcurrentandinputvoltage,fieldeffecttransistorhasanonlineartransconductancecurves.Thisisveryimportant,whichindicatesthatthepipewilldistorttheinputsignal.Distortionisnotalwaysabadthing,suchasaradiomixeristheuseofthefieldeffectisbetterthanthecharacteristicsoftheBJTtoplete.viewSTYLEREF1\s4-SEQ圖\*ARABIC\s14InputresistanceofJFETAsweknow,PNhasahighresistancewhenitisbiased.WhenJFETisworking,thePnjunctionbetweenthegatesourceisreversebiased.Therefore,thegateinputresistanceisveryhigh.ItisthisveryhighinputresistancethatbeesthemaximumadvantageoftheBJToverthebaseJFET.JFETparametertableisoftenusedinagatesourcevoltagevaluecorrespondingtothegatereversecurrentIGSStoindicatethesizeoftheinputresistance,inputresistancecanbeobtainedbythefollowingequation.Twoverticallinesrepresenttheabsolutevalue.Intheparametertableabove,Vgsis15V,andIGSSisthemaximumvalueof-1..RIN===15Asseenfromtheresults,theinputresistanceofJFETisquitehigh.Butinpracticalapplications,thetotalinputresistanceshouldalsocontainaresistancethatisconnectedtothegate,sothetotalinputresistanceshouldbeintherangeof1~10M.DifferentialamplifierDifferentialamplifierisanimportantamplifierwithmultipleapplications.Inparticular,theopampisaninputstage.Thenameofthedifferentialamplifierisderivedfromthedifferencebetweentheinputsignalwhichisaddedatthetwoinputterminals,thatis,thedifferencebetweenthetwosignals.Thesamesignalisnotamplifiedintheinput.Ithasanimportantcharacteristictoreducethemonmodenoise.Unlikeotheramplifiers,thisamplifierhastwoinputsandtwooutputs.Thepipeswerecarefullymatchedandhadthesamecharacteristics.viewSTYLEREF1\s4-SEQ圖\*ARABIC\s15Inordertounderstanditsworkingprinciple,itisassumedthatthetwobasesaregrounded.Becausethepressuredropofthebaseemitterstructureisthediodevoltagedrop,theemittervoltageis-0.7V.Theemittercurrentonbothsidesisequal,equaltohalfofthecurrentinthemonemitterresistance.Thecollectorcurrentofeachtubeisequaltothatoftheemittercurrent,whichisequaltothehalfoftheemitterresistancecurrent.Becausethecollectorcurrentisequal,thecollectorvoltageisequal.BasicOp-AmpCircuitsparatorsTheopampisusedasanonlinearelementtoparethemagnitudeofthetwovoltage.Inthisapplication,theoperationalamplifierisusingopenloop,aninputterminalisconnectedwithaninputvoltage,anotherinputendisconnectedwithareferencevoltage.Nowwetalkaboutseveralbasicparisoncircuits.viewSTYLEREF1\s5-SEQ圖\*ARABIC\s11Aparatorisanopencircuitthatisusedtoparetwoinputvoltagesandgeneratetwovaluescorrespondingtotheinputsize.Anapplicationofanoperationalparatoristomeasurewhethertheinputvoltageisbeyondacertainvalue.Duetooperationalamplifierhasaveryhighopenloopvoltagegain,sothedifferentialmodevoltagebetweenthetwoinputendsofthesmallwillsaturatetheamplifier,theoutputvoltagereachesthelimitvalue.Tested,whenthesinewaveisnegative,theoutputreachesthemaximumnegativevalue.Whenthesinewavepasseszero,theamplifierisforcedtoentertheoppositestate,andtheoutputbeesthemaximumintegrity.Itcanbeseenthatthezerocrossingparatorcanbeusedasasquarewavecircuit,withasinewavegeneratedbyFangBo.Withtheabovezerocrossingparatorisnotthesame,non-zeroparator.Afixedreferencevoltageonthereverseinputofthezerocrossingparatorcanbemodifiedintoapositiveandnegativevoltageparator.Itismorepracticalthanzero.Heusesavoltagedividertosetthereferencevoltageto:VREF=R2/R1+R2〔+v〕Amongthem,+Visthepositivesupplyvoltageamplifier,withzenerdiodesetreferencevoltage(VREF=VZ).AslongastheinputvoltageVinislessthanthereferencevoltage,theoutputwillremainthemaximumnegativevalue.Whentheinputvoltageexceedsthereferencevoltage,theoutputreachesthemaximumvalue.TheEffectofNoiseonTheparatorInmanypracticalsituations,noisecanbegeneratedontheinputline.Noisevoltagesuperimposedontheinputvoltage,willmaketheparatorerrortochangetheoutputstate.Inordertounderstandtheeffectofnoiseonvoltage,weaddalowfrequencysinusoidalvoltagetotheinputofthezerocrossingparator.Observedwiththenoiseofthesinewavewiththecorrespondingoutputwaveform,canbeseen,whenthesinewavereached0,duetothepresenceofnoisesothatthetotalinputin0toseveralchanges,resultinginthewrongoutput.Mingledwiththenoiseoftheinputwillcausetheerroroftheoutputvoltage,becauseofthesameinputvoltagevalue,paratorOPmayfromnegativeoutputstatevariabletothepositiveoutputstate,mayalsobecausedbyachangeintheoppositedirection,i.e.fromtherightpathnegative.Thisunstableconditionoccursnearthereferencevoltage,andasmallnoisefluctuationcausestheparatortochangefromonestatetotheother.Inorderthat