自动化专业外文翻译--运算放大器

UNIT 2 A: The Operational Amplifier One problem with electronic devi__

UNIT2 A:TheOperationalAmplifier Oneproblemwithelectronicdevi__scorrespondingtothegeneralized amplifiersisthatthegains,AuorA~,dependuponinternalpropertiesofthe two-portsystem(p,fl,R~,Ro,etc.)?~This__kesdesigndifficultsin__these parametersusuallyvaryfromdevi__todevi__,aswellaswithtemperature.The operationalamplifier,orOp-Amp,isdesignedtominimizethisdependen__andto __ximizetheeaseofdesign.AnOp-Ampisanintegratedcircuitthathas__ny componentpartsuchasresistorsandtransistorsbuiltintothedevi__.Atthispoint wewill__kenoattempttodescribetheseinnerworkings. Atotallygeneral____ysisoftheOp-Ampisbeyondthescopeofsometexts. Wewillinsteadstudyoneexampleindetail,thenpresentthetwoOp-Amplaws andshowhowtheycanbeusedfor____ysisin__nypracticalcircuitapplications. Thesetwoprinciplesallowonetodesign__nycircuitswithoutadetailed understandingofthedevi__physics.Hen__,Op-Ampsarequiteusefulfor researchersinavarietyoftechnicalfieldswhoneedtobuild______amplifiersbut donotwanttodesignatthetransistorlevel.Inthetextsofelectricalcircuitsand electronicstheywillalsoshowhowtobuild______filtercircuitsusingOp-Amps. Thetransistoramplifiers,whicharethebuildingblocksfromwhichOp-Amp integratedcircuitsareconstructed,willbediscussed. ThesymbolusedforanidealOp-AmpisshowninFig.1-2A-1.Onlythree connectionsareshown:thepositiveandnegativeinputs,andtheoutput.Not shownareotherconnectionsne__ssarytoruntheOp-Ampsuchasits attachmentstopowersuppliesandtogroundpotential.Thelatterconnectionsare ne__ssarytousetheOp-Ampinapracticalcircuitbutarenotne__ssarywhen consideringtheideal0p-Ampapplicationswestudyinthischapter.Thevoltagesat thetwoinputsandtheoutputwillbe representedbythesymbolsU+,U-,andUo.Eachismeasuredwithrespectt~ groundpotential.Operationalamplifiersaredifferentialdevi__s.Bythiswemean thattheoutputvoltagewithrespecttogroundisgivenbytheexpression Uo=A(U+-U-)(1-2A-l) whereAisthegainoftheOp-AmpandU+andU-thevoltagesatinputs. Inotherwords,theoutputvoltageisAtimesthedifferen__inpotentialbetween thetwoinputs. Integratedcircuittechnologyallowsconstructionof__nyamplifiercircuitsona singlecomposite"chip"ofsemiconductor__terial.Onekeytothesuc__ssofan operationalamplifieristhe"cascading"ofanumberoftransistoramplifiersto createaverylargetotalgain.Thatis,thenumberAinEq.(1-2A-1)canbeon