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APPLICATIONNOTEAN-010NITRONEXCORPORATION1JUNE2008GaNEssentials™AN-010:GaNforLDMOSUsersAPPLICATIONNOTEAN-010NITRONEXCORPORATION2JUNE2008GaNEssentials:GaNforLDMOSUsers1.TableofContents1.TABLEOFCONTENTS...................................................................................................................................22.ABSTRACT.........................................................................................................................................................3IMPEDANCEPROFILES..........................................................................................................................................32.1.INPUTIMPEDANCE....................................................................................................................................32.2.OUTPUTIMPEDANCE................................................................................................................................43.STABILITY.........................................................................................................................................................54.CAPACITANCEVS.VOLTAGE...................................................................................................................64.1.TYPICALCAPACITANCE-VOLTAGE(CV)CHARACTERISTICS................................................................64.2.OUTPUTCAPACITANCECOMPARISONBETWEENGANANDLDMOS..................................................75.BIASCIRCUITS.................................................................................................................................................75.1.GENERALBIASCOMMENTS.....................................................................................................................75.2.GATEBIAS................................................................................................................................................85.3.DRAINBIAS..............................................................................................................................................86.THERMALPRECAUATIONS........................................................................................................................86.1.TEMPERATURECOMPENSATION..............................................................................................................86.2.LINEARITYSENSITIVITYTOBIAS............................................................................................................97.SATURATEDPOWERANDCOMPRESSION..........................................................................................97.1.TYPICALCOMPRESSIONCURVES.............................................................................................................97.2.GANINLINEARITYCORRECTIONSYSTEMS..........................................................................................108.ROBUSTNESS..................................................................................................................................................108.1.OUTPUTVSWRTESTING......................................................................................................................119.MAXIMUMRFDRIVE..................................................................................................................................1110.INSERTIONPHASEVARIATION................................................................................................1310.1.WAFERANDDEVICEVARIATION..........................................................................................................1310.2.PHASEVARIATIONINTOCOMPRESSION................................................................................................1410.3.PHASEVARIATIONOVERSUPPLYVOLTAGE.........................................................................................1511.CONCLUSIONS.................................................................................................................................15APPLICATIONNOTEAN-010NITRONEXCORPORATION3JUNE20082.AbstractThisapplicationnotewillcompareLDMOSversusGaNforRFpoweramplifierstages.Basicconcepts/approximationsusedforLDMOSwillbeshowntoholdtrueforGaN.Acomparisonofequivalentoutputpowerdeviceswillbedone.ThiscomparisonwillshowsomeofthesimilaritiesofGaNandLDMOS.Differenceswillalsobeshown.KeydifferencetobeillustratedwillbethesaturationcharacteristicsofGaN.Basiccharacteristicssuchasruggedness,stabilityandcombiningmultipleamplifierstageswillalsobepresented.AdditionalpropertiesofGaNthataresignificantlydifferentthanLDMOSwillbepresented.Oneoftheseareasischargetrappingeffects,inwhichthedevicestartstoturnoff.AnothercharacteristicofGaNthatissignificantlydifferentisthebehaviorofgatecurrentnearsaturation.ImpedanceProfiles2.1.InputImpedanceInputimpedancesofGaNdevicescanbeestimatedandmodeledidenticallytoLDMOSandGaAsFETs.ThetwocommontechniquesarebasedonS-parametersandsmallsignalmodels.Notethatthisisapplicabletodeviceswithoutinternalinputmatchingnetworks.S1