This　paper　presents　a　capacitor-less　CMOS　low　dropout　regulator　(LDO)　with　a　push-pull　class　AB　amplifier,　and　a　fast　transient　controller　to　achieve　a　better　transient　response.　The　undershoot/overshoot　voltage　and　the　settling　time　are　effectively　reduced.　Through　the　theoretical　analysis　of　the　circuit,　cadence　simulation　with　SMIC　0.18μm　process　and　under　the　condition　of　the　input　voltage　range　1.4~4　V　shows　the　output　voltage　is　1.2　V,　with　the　fast　controller　the　total　quiescent　current　is　8.2　μA,　the　undershoot　/overshoot　voltage　is　97　mV/47　mV　and　the　settling　time　is　0.3　μs　as　load　current　suddenly　changes　from　1　to　100　mA,　or　vice　versa.　Compared　with　this　paper　without　fast　transient　controller,　the　undershoot　voltage,　the　overshoot　voltage　and　the　settling　time　are　enhanced　by　30%,　64%　and　80%,　respectively.　©　(2014)　Trans　Tech　Publications,　Switzerland.