design of a two-channel solid-state一个双通道固态设计

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1、211.IntroductionTheprojectinvolveddesigningandconstructingahigh-fidelityClass-Aamplifier.Designwassolid-statebasedandbiasedwithaconstantcurrentsourceinapush-pullconfiguration.Thefinalproductistobecompatibleforusewithanyconventionalaudioinput,whichhasbeenpre-amplified,andoutputistob

2、ecoupledthroughconventional8Wspeakers.Thechoiceofsolid-stateovervacuumtubesislargelybecausesolid-stateamplifiersaremoredynamicinnature,andarehencebetterabletoamplifyfrequenciesinthelowtomid-range,andbecausesolid-stateamplifiersaremorecosteffectiveAgoodpairofmatchedMOSFETswillcostap

3、proximately$20whereasamatchedpairoftubescanrunintohundredsofdollars.andhavelowermaintenanceDependingonusage,tubesneedtobechangedonceeveryonetotwoyearswhilesolid-stateamplifiersarerelativelymaintenancefree.coststhantheircounterparts.1.1OverviewofOutputClassificationsOutputstagesofam

4、plifiersareclassifiedaccordingtothestandardsshowninTable1.1.Table1.1ClassificationofOutputStagesClassDefinitionALinearoperationwith360°operationofasinewave.Operatingpointissetataboutthecenteroftheoperatingrangeandinoperation,theoutputsignalproducesapproximatelyequalexcursionstoward

5、sthetwoaxesBTransistorsarebiasedtocut-off,suchthatonly180°conductioncanoccur.“Push-pull”operationisnecessarywitheachhalfoftheoutputamplifieralternatelysupplyingthetwohalvesoftheoutputsignal.ABSmallforwardbiasandoutputstagesarenotcompletelycut-off.CStageisbiasedbeyondcut-off,allowin

6、glessthan180°conduction.211.2Class-AOperationClass-Agenerallyoffersthelowestdistortionamongtheoutputclassesandsincehighfidelityandlowdistortionisdesiredforthisproject,thedesignisbasedonClass-Aoperation.TheprimaryvirtueofClass-Aliesinthesmoothcharacteristicsofitsoperationparameters.

7、Thegaintransistorsareoperatedinthelinearregiononly,wheredistortionsarelimitedtosmooth,simpleforms,unlikeabruptdistortionscreatedinClass-Bamplifierswhenthetransistorsswitchonandoff.InClass-Aoperation,transistorsarealwayson,andthiseliminatestheturn-on/turn-offdelaysthatcharacterizeth

8、ecrossoverofClass-BandClas