模拟电子技术基础(论文)

..摘要模拟电子技术是一门研究对仿真信号处理的模拟电路学科。模拟电路作为电气工程及其自动化专业主干课程之一，经历了长足的发，目前已经被广泛应用在我们的生活中。模拟电子技术以半导体二极管、半导体三极管和场效应管为关键电子器件，包括功率放大电路、运算放大电路、反应放大电路、信号运算与处理电路、信号产生电路、电源稳压电路等研究方向，不断的改革创新，并应用到生产生活当中，极大的推动了科技的进步。本文概述了模拟电子技术的开展过程及其前景，接着对模拟电子技术根底每章节进展双语详解，从而到达深层次理解掌握模拟电子技术的目的。关键词:模拟电子技术，二极管，信号发生器..ABSTRACTElectronic

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technology.Keywords:Analogelectronictechnology;triode;teaching;signalcircu..绪论简介模拟电子技术是电子技术的一个方面,他是一个非常美丽的地方,在这个领域,数学、物理、信息工程、电气工程和自动化工程学科发现和谐集成点,其深刻的理论根底和广泛的实际应用使它有一个强大而持久的生命力。因此,对于许多相关的科学。模拟电子技术是一个非常重要的根底理论课程。一般来说,模拟电子技术是一个实用的,非常实用的课题,本文的主要目的是研究各种半导体器件的性能、电路及其应用,模拟电子技术,很多的概念,但在科学和工程专业知识的过程中学习。起着非常重要的作用,它不仅是为未来的课程奠定根底,为我们分析和解决问题的能力也是非常重要的。根据目前流行的说,就是使用一门外语(主要是英语)进展非语言学科的教学,为学生创造一个密切接触英语环境〞。认为,双语教学被认为是一种外语教学方法不够全面。在当今世界,有很多多元文化国家根据实际情况,在一些学校实施双语教学,双语教学是它的目的,主要是指一个语言政策是一个多元文化的国家,而不仅仅是一种教学方式。双语教学改革的实施不仅有利于培养素质高、能力强,而且教师的英语水平的提高。作为一个重要的专业电工根底课程,实施双语教学是最好的选择。模拟电子技术课程的双语教学模式,经过一系列的教学实践和探索实践证明效果是比拟理想的,可以更好地扩大学生的知识,提高学习能力。根据双语教学的模式,不仅让学生根据其根本原理来解决遇到的问题的过程中学习和英语水平的提高,增强学生的学习兴趣,让他们觉得有用。模拟电子技术课程的教学目标。模拟电子技术的特点是:线性和非线性的组合,直流和交流,结合电路和设备,根本的估计和物理概念的组合。目前,模拟电子技术的现状可以简单地鬼说:理论体系和严密整合,全面介绍网络图论,通过计算机的影响,非线性电路与系统的研究方兴未艾,集成电路和超大规模的快速开展的状态将在很长一段时间对电路和系统科学的开展,在多通道设备,集成;在系统的分析方法,优化集成;在系统扩展从线性到非线性,从被动到主动,从单一元素离散扩展到集成电路系统。进入21世纪,电子技术快速开展的时代,随着技术的不断改良,使设备规模继续缩小,以不断提高集成,降低功耗,旗舰性能得到了改良。随着时代的开展,将越来越多的双语教学教师和所有年龄段的学生,一方面可以提高语言能力,另一个是与世界先进的电子技术知识的整合,扩大我们的视野,与英语的国际化和电子技术的快速开展,传统的刚性的教学将逐步新颖便捷的多媒体技术来取代。多媒体课件的教学方法是一个根本出发点是基于文本、图像、声音、动画和其他方式合作,刺激学生的感官,激发学生的兴趣和严格的形式的多媒体课件和黑板,粉笔是没有区别,获得教学效果并不显著。课件的制作适当的材料,适用于木材。多媒体课件可以充分发挥学生的潜能,强化教学效果,提高教学质量为重心。但最终多媒体只是一种辅助教学手段,为了更好地利用先进的知识传播工具。课题来源随着当今世界的开展，外语的应用越来越广泛，国外语环境较差。所以教育需要创新，为此我们学校领导及教师让我们以双语课件为主题写一篇论文。双语教学不仅可以让学生与英语有亲密的环境，也能让教师的整体素质能力得到提高。在中国这个多元化国家，双语教学不仅是一种教学模式，更是一种语言政策。模拟电子技术作为一门电类相关专业的重要专业根底教程之一，实施双语教学模式是非常适宜的。课题研究目的及意义对于这次模拟电子技术根底使用双语教学模式，我们主要目的是能让学生在学习的过程中可以掌握两种语言，提高对英语的理解，增强学习兴趣，扩大学生的知识面。经过一系列研究实践和探索，双语教学的效果理想，不仅专业上学以致用，外语能力也得到提高，学习也更加有兴趣了。这就是模拟电子技术双语教学的目的所在了。国研究现状和开展趋势及综述模拟电子技术的特点为：线性与非线性相结合，直流与交流相结合，电路与器件相结合，根本估算与物理概念相结合。目前，模拟电子技术的现状可简单地鬼难为：与系统理论严密结合、全面引入网络图论、深受计算机的冲击、非线性电路与系统的研究方兴未艾、集成电路的出现并向超大规模迅速开展的状况将在相当长时间左右电路与系统学科的开展；在器件上多段话、集成化；在分析方法上系统化、最正确化、可集成化；在体系上从线性扩展到非线性、从无源扩展到有源、从单元件分立扩展到电路系统的集成。进入21实际，电子技术进入了飞速开展的时代，随着工艺技术的不断改良，使得器件的尺寸不断缩小，从而集成度不断提高，功耗降低，旗舰性能得到提高。..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图\*ARABIC\s11Inordertomakethesignalcarryinginformationtransmission,electronicwaveformofthevoltageorfrequencyofsomeenergyneedstochange,tele,generalwillinafixedtimeintervalrepeat,therepetitivewaveformcalledperiodicwaveform.Cycleisthetimerequiredtopleteacyclewaveform.Whichisdividedintomanykindsofwaves,suchassinewave.viewSTYLEREF1\s2-SEQ图\*ARABIC\s12Sinewaveisthemostbasicandmostimportantwaveform.Itisthewaveformofthecurrentorvoltage,withthesamewaveformasthetrigonometricfunctionofthesinwaveinthealgebra.SinewaveisakindofwaveformwhichcanbenaturallygeneratedbyACgeneratororradiowave.Italsohaslasergeneratingprocess,sonicvibrationphenomenonviewSTYLEREF1\s2-SEQ图\*ARABIC\s13ThePNJunctionAPNjunctionisadiode.Intheequilibriumstate,thereisnocurrentinthePNjunction.Themainuseofthesemiconductordiodeistheonewayelectricconductivity.viewSTYLEREF1\s2-SEQ图\*ARABIC\s14PNjunctionWhenapuresemiconductorisgenerallydopedntype,thegeneraldopingofPtype,theninbetweenthetworegionsontheformationofaPNnode.IntheNarea,therearemanyfreeelectronsandseveralholeswhicharethermallyproduced.Therearemanyholesinthepregion.Thefreeelectron.Pnstructureproducedbythehotelectronsisthebasicdiodeandthebasisoftheworkofallsolidstateponents.Diodeisaponentthatonlyallowscurrenttoflowinonedirection.viewSTYLEREF1\s2-SEQ图\*ARABIC\s15BiasingtheSemiconductorDiodeThetermbiasinelectronicsreferstoafixedDCvoltagewhichisaddedtothesemiconductorelementtosetitsworkingconditions.ForwardbiasistheconditionthatallowsthecurrenttoflowthroughthePNjunction.ReversebiasisthebiasconditiontopreventthecurrentflowingthroughthePNjunction.Asshowninthefollowingfigure.TheleadoutofthePregioniscalledapositiveelectrodeorananode,andtheleadoutoftheNregioniscalledanegativeelectrodeoracathode3.4 DiodeclassificationviewSTYLEREF1\s2-SEQ图\*ARABIC\s16Diodeclassificationphotodiode:Thereversecurrentincreaseswiththeincreaseoftheintensityoflight.viewSTYLEREF1\s2-SEQ图\*ARABIC\s17Whenaforwardcurrentflows,thelightofacertainwavelengthrangeissentout,andthecurrentlightemittingtubecanemitlightfrominfraredtovisiblelightband.viewSTYLEREF1\s2-SEQ图\*ARABIC\s18BipolarJunctionTransistorsStructureofBipolarJunctionTransistorsBipolartransistor,itisabbreviatedasBJT.Isconstructedfromthreedopedsemiconductorregions.Thesethreeregionsareknownastheemissionregion,thebaseregionandthecollectorregion(FigureA,b);viewSTYLEREF1\s3-SEQ图\*ARABIC\s11thesethreeregionsareseparatedbytwopn.Weknowthatbipolartransistorsaredividedintotwotypes.OneofthetwoPnareasinthemiddleofaPNwithathinlayer,knownasNPNtypetransistor,thereisatwoPNarea,themiddleofathinlayerofPNclip,calledPNPtypetransistor.Thesetwokindsoftransistorsarewidelyusedbyus,buttheformerismorewidelyused.Somostofuslearnaboutit.viewSTYLEREF1\s3-SEQ图\*ARABIC\s12TransistoroperatingprincipleInordertomakethetransistorworknormally,anexternalDCbiasvoltagemustbeprovidedontwoPnjunctionsinordertoestablishtheproperworkingconditions.NPNandPNPtubenormalbias,intwocases,thelaunchofthejunctionareforwardbias,theseasonisreversebias,knownaspositiveandnegativebias.viewSTYLEREF1\s3-SEQ图\*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图\*ARABIC\s14viewSTYLEREF1\s3-SEQ图\*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图\*ARABIC\s11Fieldeffecttubeis,referredtoasFET.Itisatypeofsemiconductordevice,anditsworkingprincipleispletelydifferentfromthepreviousBJT.Inthefieldeffecttube,theconductivepropertyofanarrowlongconductivechanneliscontrolledbyapowerplant,whichisformedbyaddingthethirdpolegrid.Itcanbedividedintotwoclasses:thefirstclass:thejunctiontypefieldeffecttube,whichischaracterizedbytheformationofaPNjunctionbetweenthegateandthechannelofthetube.Secondclass:thisclassiscalledmetaloxidesemiconductorfieldeffecttransistor,whichisusedtocontroltheelectricalconductivityofthechannel,theinsulationlayerisaverythinlayerofglass.viewSTYLEREF1\s4-SEQ图\*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图\*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图\*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图\*ARABIC\s15Inordertounderstanditsworkingprinciple,itisassumedthatthetwobasesaregrounded.Becausethepressuredropofthebaseemitterstructureisthediodevoltagedrop,theemittervoltageis-0.7V.Theemittercurrentonbothsidesisequal,equaltohalfofthecurrentinthemonemitterresistance.Thecollectorcurrentofeachtubeisequaltothatoftheemittercurrent,whichisequaltothehalfoftheemitterresistancecurrent.Becausethecollectorcurrentisequal,thecollectorvoltageisequal.BasicOp-AmpCircuitsparatorsTheopampisusedasanonlinearelementtoparethemagnitudeofthetwovoltage.Inthisapplication,theoperationalamplifierisusingopenloop,aninputterminalisconnectedwithaninputvoltage,anotherinputendisconnectedwithareferencevoltage.Nowwetalkaboutseveralbasicparisoncircuits.viewSTYLEREF1\s5-SEQ图\*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