单端信号转差分信号-方法介绍

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1、CombiningInputAmplifiersandConvertersforFrequencyDomainApplicationsVeraMaoTexasInstrumentsAllHighSpeed,HighPerformanceADCshaveDifferentialInputs•Driveamplifiercircuitneedstoprovidedifferentialinputs•Ifinputsignalissingleended,mustconverttodifferential–Canbedone

2、withsingleendedAmpsandtransformers–CanbedonewithFDA(FullyDifferentialAmplifiers)•BetterperformanceifinputsignalisdifferentialSingleEndedampwithtransformerinterfaceTwofactorslimitthisapproach•Amplifier(oftennotpresent)–Single-endedarchitecturemustconsumeagreatde

3、alofpowertokeepHD2componentslow.•Transformer–Ifnoamplifier,thenlimitedchoicesinvoltagegain(viaturnsratio)–Limitslowfrequencies–Pass-bandflatnesscanbeanissuebecauseofripple.Transformers-WillnotpassDCsignalsandlossesvaryoverthepass-bandExample1:HighBWbalunExample

4、2:IsolationTransformerMacomETC1-13MinicircuitsADT1-1WTPassbandrippleLowFrequencyroll-offWillnotpassDCHigh-SpeedFDAsofferreducedpowerandcostasactiveA/Ddrivers•BroadbandFullyDifferentialAmplifiers(FDAs)–Easy&efficientwaytoprovideDC-coupledinterfacewithgain.•Lessp

5、owerconsumptionthananRFamp.•Flexiblegainoptions–GivesbestperformancewithdifferentialinputsOSIN+THS770006IN-SOSingleEndedtoDifferentialwithFDAs•Canefficientlyprovide–Gain–PerformSingleEndedtoDifferentialconversion–LevelshifttoinputcommonmodeofADCOthersingle-ende

6、d-to-differentialAmplifierConfigurations©Opampscanprovidesingle-ended-to-differentialconversionwithlowerpower&cost1.FullyDifferentialOpAmps(FDAs)RGRFSingle-Ended•Featuredifferentialinputsandoutputs,andInputVS+outputcommonmodecontrol.DifferentialRTHS4509•Provide

7、aneasymeansforDC-coupledSE-DIFFGOutputconversion.VS-®Independentoutputcommonmodecontrol.RF®MuchbetterSFDRperformanceforfullydifferentialinputs/outputs.single-ended2.DualOpAmpsforSE-DIFFconversion.input•Someoftheseworkprettywell,butcangivedifferentiamodestloutpu

8、tSFDRperformance•BestperformancelimitedtolowerfrequenciesOthersingle-ended-to-differentialAmplifierConfigurations(cont’d)3.TransformerswithDualOpAmps©Transformersprovidetheb