Accurate Two-Transistor Current Mirrors.pdf

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1、AccurateTwo-TransistorCurrentStephenW.MilamDr.PhillipE.AllenSchoolofElectricalEngineeringSchoolofElectricalEngineeringGeorgiaInstituteofTechnologyGeorgiaInstituteofTechnologyAtlanta,GA30332-0250USAAtlanta,GA30332-0250USAAbstract--Atuningmethodforcurrentmirrorshasnobetterthan1.3%forag

2、ate-sourcevoltageof2V.Thebeenproposedandtestedina2-ymCMOSprocess.samepaperreportsanoptimumdimensionfortransistorThemethodcompensatesformismatchesinboththematchingis50pm:100ym(WL).Otherresults[5]canbetransconductanceandthresholdvoltageofthetran-usedtopredictanerrorofsistors.Resultssho

3、wthatwithatransconductancetuningresolutionof0.78%andathresholdvoltagetuningresolutionof0.088%,themirrorscanbetunedtoanaverageaccuracyof0.25%eventhoughtheuntunedcircuitshavecurrentgainerrorsashighas6.59%.I.INTRODUCHONwhererepresentsthestandarddeviationoftherandomCostcanbeamajorissuewh

4、enfabricatinganintegratedvariableshownasitssubscript,andabarindicatesthemeancircuit.CMOStechnologyisattractiveforitslowcost,butvalueofarandomvariable.LandWaretheeffectivelengthtransistormismatchcandecreaseaccuracyinmanyandwidth(incm),respectively,oftheMOSFETsintheapplications.Thispap

5、erpresentsamethodforreducingthemirror,Iisthedraincurrent,VGSisthegate-sourcevoltage,inaccuraciesduetomismatchinMOStransistors.PublishedandVTisthethresholdvoltage.Usingparametersfroma2-resultsshowthatmatchinginMOSFETcurrentmirrorsisymp-wellCMOSprocessin(2)yieldsanexpectedstandardpoore

6、rthanthematchinginBJTmirrors,especiallyatlowdeviationof0.64%forV~s=1.5Vand324aspectratios.currentlevels[11.Anothersourceofmismatchisduetochannel-lengthAsignificantadvantagetotheproposedapproachisthatitmodulation,butthiserrorisonlypresentwhentheterminalcanbeusedfortransistorswithshort

7、gatelengths(4ymorvoltages,specificallythedrain-sourcevoltages,ofthetwoless),whiletraditionaldesignprinciplesrecommendlargertransistorsdiffer.Carefuldesign(i.e.,usingcascodemirrors)dimensionsforprecisionapplications.Resultsindicatethatcanrenderthiseffectinsignificant,soitisnotconsider

8、edincurrentm