设计指南电容式触摸传感器英文翻译

10无锡职业技术学院毕业设计说明书〔英文翻译〕OperationalAmplifiersIdealandPracticalModelsTheconceptoftheoperationalamplifier(usuallyreferredtoasanopamp)originatedatthebeginningoftheSecondWorldWarwith theuseofvacuumtubesindcamplifierdesignsdevelopedbytheGeorgeA.PhilbrickCo.[someoftheearly historyofoperationalamplifiersisfoundinWilliams,1991].Theopampwasthebasicbuildingblockforearlyelectronicservomechanisms,forsynthesizers,andinparticularforanalogcomputers usedtosolvedifferentialequations.Withtheadventofthefirstmonolithicintegrated-circuit(IC)opampin1965(theA709,designedbythelateBobWidlar,thenwithFairchildSemiconductor),theavailabilityofopampswasnolongerafactor,whilewithinafewyearsthecostofthesedevices(whichhadbeenashighas$200each)rapidlyplummetedtoclosetothatofindividualdiscretetransistors.Althoughthedigital computerhasnowlargelysupplantedtheanalogcomputerinmathematically intensive applications, the useof inexpensiveoperationalamplifiers instrumentation applications, in pulse shaping, in filtering, and in signal processingapplications in general hascontinued to grow. There are currently many commercialmanufacturerswhosemainproductsarehigh-qualityopamps. Thiscompetitivenesshasensuredamarketplacefeaturingawiderangeofrelativelyinexpensivedevicessuitableforusebyelectronicengineers,physicists,chemists,biologists,andalmostanydisciplinethatrequiresobtainingquantitativeanalogdatafrominstrumentedexperiments.Mostoperationalamplifiercircuitscanbeanalyzed,atleastforfirst-ordercalculations,byconsideringtheopamptobean“ideal”device.Formorequantitativeinformation,however,andparticularlywhenfrequencyresponseanddcoffsetsareimportant,onemustrefertoamore“practical”modelthatincludestheinternallimitationsofthedevice.Iftheopampischaracterizedbyareallycompletemodel,theresultingcircuitmaybequitecomplex,leadingtoratherlaboriouscalculations.Fortunately,however,computeranalysisusingtheprogramSPICEsignificantlyreducestheproblemtooneofasimpleinputspecificationtothecomputer.Today,nearlyalltheopampmanufacturersprovideSPICEmodelsfortheirlineofdevices,withexcellentcorrelationobtainedbetweenthecomputersimulationandtheactualmeasuredresults.TheIdealOpAmpAnidealoperationalamplifierisadc-coupledamplifierhavingtwoinputsandnormallyoneoutput(althoughinafewinfrequentcasestheremaybeadifferentialoutput).Theinputsaredesignatedasnoninverting(designated+orNI)andinverting(designated–orInv.).Theamplifiedsignalisthedifferentialsignal,v,betweenthetwoinputs,sothattheoutputvoltageasindicatedinFig.1is无锡职业技术学院毕业设计说明书〔英文翻译〕FIGURE1Configurationforanidealopamp.Thegeneralcharacteristicsofanidealopampcanbesummarizedasfollows:Theopen-loopgainAOLisinfinite.Or,sincetheoutputsignalvoutisfinite,thenthedifferentialinputsignalvmustapproachzero.TheinputresistanceRINisinfinite,whiletheoutputresistanceROiszero.Theamplifierhaszerocurrentattheinput(iAandiBinFig.1arezero),buttheopampcaneithersinkorsourceaninfinitecurrentattheoutput.Theopampisnotsensitivetoacommonsignalonbothinputs(i.e.,vA=vB);thus,theoutputvoltagechangeduetoacommoninputsignalwillbezero.Thiscommonsignalisreferredtoasacommonmodesignal,andmanufacturersspecifythiseffectbyanopamp’scommon-moderejectionratio(CMRR),whichrelatestheratiooftheopen-loopgain(AOL)oftheopamptothecommon-modegain(ACM).Hence,foranidealopampCMRR=.AsomewhatanalogousspecificationtotheCMRRisthepower-supplyrejectionratio(PSRR),whichrelatestheratioofapowersupplyvoltagechangetoanequivalentinputvoltagechangeproducedbythechangeinthepowersupply.Becauseanidealopampcanoperatewithanypowersupply,withoutrestriction,thenfortheidealdevicePSRR=.Thegainoftheopampisnotafunctionoffrequency.Thisimpliesaninfinitebandwidth.Althoughtheforegoingrequirementsforanidealopampappeartobeimpossibletoachievepractically,moderndevicescanquitecloselyapproximatemanyoftheseconditions.Anopampwithafield-effecttransistor(FET)ontheinputwouldcertainlynothavezeroinputcurrentandinfiniteinputresistance,butacurrentof<10pAandanRIN=1012isobtainableandisareasonableapproximationtotheidealconditions.Further,althoughaCMRRandPSRRofinfinityarenotpossible,thereareseveralcommercialopampsavailablewith of140dB(i.e.,aratioof107).Open-loopgainsofseveralprecisionopampsnowhavereachedvaluesof>107,althoughcertainlynotinfinity.Thetwomostdifficultidealconditionstoapproacharetheabilitytohandlelargeoutputcurrentsandtherequirementofagainindependencewithfrequency.Usingtheidealmodelconditionsitisquitesimpletoevaluatethetwobasicopampcircuitconfigurations,(1)theinvertingamplifierand(2)thenoninvertingamplifier,asdesignatedinFig.2.Fortheidealinvertingamplifier,sincetheopen-loopgainisinfiniteandsincetheoutputvoltagevoisfinite,thentheinputdifferentialvoltage(oftenreferredtoastheerrorsignal)vmustapproachzero,ortheinputcurrentisThefeedbackcurrentiFmustequaliI,andtheoutputvoltagemustthenbeduetothevoltagedropacrossRF,or无锡职业技术学院毕业设计说明书〔英文翻译〕FIGURE2 Illustrationof(a)theinvertingamplifierand(b)thenoninvertingamplifier.Theinvertingconnectionthushasavoltagegainvo/viof-RF/RI, aninputresistanceseenbyvIofR1ohms[fromEq.(27.2)],andanoutputresistanceof0.ByasimilaranalysisforthenoninvertingcircuitofFig.2(b),sinceviszero,thensignalvImustappearacrossresistorR1,producingacurrentofvI/R1,whichmustflowthroughresistorRF.Hencetheoutput voltage is the sum of the voltage drops acrossRF and R1 , orAsopposedtotheinvertingconnection,theinputresistanceseenbythesourcevIisnowINequaltoaninfiniteresistance,sinceR fortheidealopampisinfinite.INPracticalOpAmpsAnonidealopampischaracterizednotonlybyfiniteopen-loopgain,inputandoutput无锡职业技术学院毕业设计说明书〔英文翻译〕resistance,finitecurrents,andfrequencybandwidths,butalsobyvariousnonidealitiesduetotheconstructionoftheopampcircuitorexternalconnections.AcompletemodelforapracticalopampisillustratedinFig.3.FIGURE3 Amodelforapracticalopampillustratingnonidealeffects.ThenonidealeffectsofthePSRRandCMRRarerepresentedbytheinputseriesvoltagesourcesofVsupply/PSRRandVCM/CMRR,whereVsupplywouldbeanytotalchangeofthedctwopowersupplyvoltages,V+ andV–dc,fromtheirnominalvalues,whileVCMisthevoltagedccommontobothinputsoftheopamp.Theopen-loopgainoftheopampisnolongerinfinitebutismodeledbyanetworkoftheoutputimpedanceZout(whichmaybemerelyaresistorbutcouldalsobeaseriesR-Lnetwork)inserieswithasourceA(s),whichincludesalltheopen-looppolesandzeroesoftheopampaswhereAOListhefinitedcopen-loopgain,whilepolesareatfrequenciesp1,p2,... andzeroesareatZ1,etc.ThedifferentialinputresistanceisZIN,whichistypicallyaresistanceINparallelwithacapacitorCIN.Similarly,thecommon-modeinputimpedanceZCMisestablishedbyplacinganimpedance2ZCMinparallelwitheachinputterminal.Normally,ZCM无锡职业技术学院毕业设计说明书〔英文翻译〕isbestrepresentedbyaparallelresistanceandcapacitanceof2RCM(whichis>>RIN)andCCM/2.ThedcbiascurrentsattheinputarerepresentedbyIB+andIB–currentsourcesthatwouldequaltheinputbasecurrentsifadifferentialbipolartransistorwereusedastheinputstageoftheopamp,ortheinputgatecurrentsifFETswereused.Thefactthatthetwotransistorsoftheinputstageoftheopampmaynotbeperfectlybalancedisrepresentedbyanequivalentinputoffsetvoltagesource,VOS,inserieswiththeinput.Thesmallestsignalthatcanbeamplifiedisalwayslimitedbytheinherentrandomnoiseinternaltotheopampitself.InFig.3thenoiseeffectsarerepresentedbyanequivalentinputvoltagesource(ENV),whichwhenmultipliedbythegainoftheopampwouldequalthetotaloutputnoisepresentiftheinputstotheopilarfashion,iftheinputstotheopampwereopencircuited,thetotaloutputnoisewouldequalthesumofthenoiseduetotheequivalentinputcurrentsources(ENI+andENI–),eachmultipliedbytheirrespectivecurrentgaintotheoutput.Becausenoiseisarandomvariable,thissummationmustbeaccomplishedinasquaredfashion,i.e.,Typically,thecorrelation(C)betweentheENVandENIsourcesislow,sotheassumptionofC0canbemade.ForthebasiccircuitsofFig.27.2(a)or(b),ifthesignalsourcevIisshortedthentheoutputvoltageduetothenonidealeffectswouldbe(usingthemodelofFig.3)providedthattheloopgain(alsocalledlooptransmissioninmanytexts)isrelatedbytheinequalityInherentinEq.(27.8)istheusualconditionthatR1<<ZINandZCM.IfaresistorR2wereinserieswiththenoninvertinginputterminal,thenacorrespondingtermmustbeaddedtotheofvalue–IB+R2(R1+RF)/R1.Onmanufacturers’datasheetstheindividualvaluesofIB+andIB–arenotstated;insteadtheaverageinputbiascurrentandoffsetcurrentarespecifiedasTheoutputnoiseeffectscanbeobtainedusingthemodelofFig.3alongwiththecircuitsofFig.2aswhereitisassumedthataresistorR2isalsoinserieswiththenoninvertinginputofeitherFig.2(a)or(b).Thethermalnoise(oftencalledJohnsonorNyquistnoise)duetotheresistorsR1,R2,andRFisgivenby(inrmsvolt2/Hz)无锡职业技术学院毕业设计说明书〔英文翻译〕wherekisBoltzmann’sconstantandTisabsolutetemperature(Kelvin).Toobtainthetotaloutputnoise,onemustmultiplytheE2outexpressionofEq.(27.10)bythenoisebandwidthofthecircuit,whichtypicallyisequalto/2timesthe–3dBsignalbandwidth,forasingle-poleresponsesystem[Kennedy,1988].SPICEComputerModelsTheuseofopampscanbeconsiderablysimplifiedbycomputer-aidedanalysisusingtheprogramSPICE.SPICEoriginatedwiththeUniversityofCalifornia,Berkeley,in1975[Nagel,1975],althoughmorerecentuser-friendlycommercialversionsarenowavailablesuchasHSPICE,HPSPICE,IS-SPICE,PSPICE,andZSPICE,tomentionfewofthosemostwidelyused.Asimplemacromodelforanear-idealopampcouldbesimplystatedwiththeSPICEsubcircuitfile(*indicatesacommentthatisnotprocessedbythefile).SUBCKTIDEALOA123*Anear-idealopamp:(1)isnoninv,(2)isinv,and(3)isoutput.RIN121E12E1(3,0)(1,2)1E8.ENDSIDEALOA(27.12)ThecircuitmodelforIDEALOAwouldappearasinFig.4(a).Amorecompletemodel,butnotincludingnonidealoffseteffects,couldbeconstructedforthe741opampasthesubcircuitfileOA741,showninFig.4(b)..SUBCKTOA741126*Alinearmodelforthe741opamp:(1)isnoninv,(2)isinv,and*(6)isoutput.RIN=2MEG,AOL=200,000,ROUT=75ohm,*Dominantopen-looppoleat5Hz,gain-bandwidthproduct*is1MHz.RIN122MEGE1(3,0)(1,2)2E5R134100KC1400.318UF;R12C1=5HZPOLEE2(5,0)(4,0)1.0ROUT5675.ENDSOA741(27.13)ThemostwidelyusedopampmacromodelthatincludesdcoffseteffectsistheBoylemodel[Boyleetal.,1974].Mostopampmanufacturersusethismodel,usuallywithadditionstoaddmorepoles(andperhaps zeroes).Thevariousresistorandcapacitorvalues,aswellastransistor,andcurrentandvoltagegenerator,valuesareintimatelyrelatedtothespecificationsoftheopamp,asshownearlierinthenonidealmodelofFig.3.Theappropriateequationsaretooinvolvedtolisthere;instead,theinterestedreaderisreferredtothearticlebyBoyle inthelistedreferences.TheBoylemodeldoesnotaccuratelymodelnoiseeffects,nordoesitfullymodelPSRRandCMRReffects.Amorecircuits-orientedapproachtomodelingopampscanbeobtainediftheinputtransistorsareremovedandamodelformedbyusingpassivecomponentsalongwithbothfixedanddependentvoltageandcurrentsources.Thismodelnotonlyincludesallthebasicnonidealeffectsoftheopamp,allowingformultiplepolesandzeroes,butcanalsoaccuratelyincludeENVandENInoiseeffects.无锡职业技术学院毕业设计说明书〔英文翻译〕无锡职业技术学院毕业设计说明书〔英文翻译〕Thecircuits-approachmacromodelcanalsobeeasilyadaptedtocurrent-feedbackopampdesigns,whoseinputimpedanceatthenoninvertinginputismuchgreaterthanthatattheinvertinginput[seeWilliams,1991].TheinterestedreaderisreferredtothetexteditedbyJ.Williams,listedinthereferences,aswellastheSPICEmodelingbookbyConnellyandChoi[1992].无锡职业技术学院毕业设计说明书〔英文翻译〕运算放大器运算放大器〔通常称之为opamp〕的概念起源于其次次世界大战开头时，乔治•a菲1991年在威廉姆斯被觉察•后由飞兆半导体公司设计)在1965〔它曾经有过200美元/个的高价〕使得运算放大器的可利用性不再是一个要素。个别的分别晶体管销量快速下滑。尽管现在数字式计算机在数学上的密集应用领域大量取代了模拟计算机，廉价的运放用于设备的应用、脉冲的整形、过滤和信号进程应用方面正普遍的持续增长。目前消灭了很多主要生产高质量运放的制造商。这些竞争确保了以相比较而言廉价的适合于电子工程师、物理学家、化学家、生物学家以及大局部要获得大量从仪器试验中得到模拟资料的学科。考虑到运放是初级装置，大局部运放电路是能够分析的，至少对于初级计算而言。然而，对于更多的数量信息，特别是频率响应和直流补偿重要的时候，它必需受该设备内部限制的更加实际的模型。当运放是一个以真正简洁的模型为特征时，信号寄生回路引起的直流接地假象将会格外简洁。倾向于在确定程度上的困难的计算。幸运的是，然今日，几乎全部的运放制造商为他们设备的线路供给SPICE模型，获得了电脑模拟和实际测量结果之间的精彩的相互关系。抱负运算放大器抱负运算放大器是直流耦合放大器，拥有两个输入端，通常只有一个输出端〔尽管〔设计为正极或网络接口〕和反相此，输出电压如图1中所示1抱负运放的构造抱负运放的普遍特点可以总结如下：i开环增益AOL是无限的，或者说，由于输出信号vout是有限的，所以不同的输入信号v必需接近0.i输入电阻RIN是无限的，输出电阻R0为0.运放输入端电流为0〔图1中的A和i为0，但运放是输出端无限电流的来源。B(vAvB)无锡职业技术学院毕业设计说明书〔英文翻译〕于运放的共模抑制比〔它是运放的开环增益AOL与共模增益A 的比率〕形成的；因CM此，对于抱负运放的共模抑制比为无穷大。电阻，所以抱负装置PSRR为无穷大。运放的增益不是频率的功能，这说明它有无穷的带宽。尽管前面提到的对抱负运放的要求在实际实现中是不行能的，现在的设备能格外接一个小于10pA的电流和一个RIN=1012 的电阻是可获得的，并且近似为抱负状况是合理尽管确定不是无限的，但一些准确的运放的开环增益已超过107的数量级。两种接近的理想最困难状况是应对大输出电流力气和不依靠频率的增益的要求。〔2〕2中设计的。；对于抱负反相放大器，由于开环增益是无限的，并且由于输出电压是有限的，因此，输入不同的〔通常指错误的信号〕v0，或输入电流是；无锡职业技术学院毕业设计说明书〔英文翻译〕2反相放大器和非反相放大器的插图反相连接这样便有了一个电压增益v/v为-R/R 抗可以从R上的v

看出，o i F I， 1 I并且输出阻抗为0欧姆。对于非反相电路的分析是相像的，如图2〔b〕所示，因此，因v0，信号v必需高于Rv/R

R

从今处，输出电i i I压是在R 和R上流掉的电压之和，或是

I 1， F。F 1i相反，对于反相连接，源电压vi

时的输入阻抗现在为无限大。实际运算放大器非抱负运放不仅以有限的开环增益、有限的输入输出电阻、有限的电流、有限的频率带宽为特征，并且很多非抱负状态是运放的电路或外部连接的建筑。实际运放的一个3中插图所示。无锡职业技术学院毕业设计说明书〔英文翻译〕3说明非抱负影响的实际运算放大器模型PSRR和CMRR的非抱负影响通过输入系列电压源DVsupply/PSRR和VCM/CMRR表现出来，DVsupplyVdc+和Vdc-这两个微缺乏道数值的总计转变量，此时，VCM为运放两个输入端共同拥有。运放的开环增益不再是无限的,Zout(它可能仅仅是一个电阻,但也可能是一个系列R-L其中包括了运放全部的开环极点和零点如,wp1,wp2,...且零点在wZ1等。IN〔INCIN的并联，同样,2ZCM,ZCM是最能代表平衡电阻2R 〔远大于R )和电容C /2。输入端的直流偏置电流通过I+ 和I-电源表示，CM IN CM