pFET Linear Regulator Has Low Dropout Voltage

P-channelMOSFETs(pFETs),thoughmoreexpensivethanpnptransistors,arefreeofthedissipationlossassociatedwithbasedriveinapnpcircuit.pFETsalsohavealowersaturationvoltageatlightloads(Figure1).Infact,thelowRDS(ON),logic-level,p-channelpowerMOSFETscurrentlyavailablecanregulate5Vfroma5.1Vbattery!Maxim>AppNotes>AmplifierandComparatorCircuitsVoltageReferencesKeywords:P-FET,linearregulator,lowdropout,p-channel,MOSFETs,amplifiers,comparatorJul09,1998APPLICATIONNOTE103pFETLinearRegulatorHasLowDropoutVoltageP-channelMOSFETs(pFETs),thoughmoreexpensivethanpnptransistors,arefreeofthedissipationlossassociatedwithbasedriveinapnpcircuit.pFETsalsohavealowersaturationvoltageatlightloads(Figure1).Infact,thelowRDS(ON),logic-level,p-channelpowerMOSFETscurrentlyavailablecanregulate5Vfroma5.1Vbattery!Figure1.Ap-channelMOSFET(Q1)allowsthislinearregulatortooperatewithVINtoVOUTdifferentialslowerthan100mV.ThiscapabilityletstheFigure2circuitderive5V±10%