This　paper　presents　a　bandgap　reference　and　an　output-capacitorless　LDO　regulator　with　adaptive　power　transistors.　The　bandgap　reference　consists　of　a　current　reference　circuit,　a　bipolar　transistor　and　proportional-to-absolute-temperature　(PTAT)　voltage　generators.　The　proposed　LDO　improves　load　transient　and　light　load　efficiency　by　permitting　the　regulator　to　transform　itself　between　2-stage　and　3-stage　topologies,　depending　on　the　load　current　condition.　Cadence　simulation　with　SMIC　0.18　μm　process　shows　that　the　bandgap　reference　generates　a　reference　voltage　569　mV　and　the　quiescent　current　is　only　0.23　μA,　the　proposed　LDO　generates　an　output　voltage　1　V,　the　quiescent　current　is　0.88　μA　(including　bandgap　reference)　at　no-load　condition,　the　undershoot/overshoot　voltage　is　187　mV/152　mV　and　the　settling　time　is　5　μs　as　load　current　suddenly　changes　from　0　to　100　mA,　or　vice　versa.　©　2014　Trans　Tech　Publications,　Switzerland.