A CMOS Low-Dropout Regulator With a Momentarily Current-Boosting Voltage Buffer

An energy-efficient voltage buffer for a low-dropout regulator ( LDO) is presented in this paper. The voltage buffer contains a current-boosting circuit with quick-on and auto-off features so that it can momentarily provide an extra current to charge and discharge the large gate capacitance of the power transistor. The voltage buffer is therefore able to increase the slew rate at the gate of the power transistor, whereas the quiescent current of the LDO remains constantly low in the steady state. Moreover, the proposed current-boosting circuit has a capacitive shunt feedback network to improve the loop bandwidth of the LDO. The proposed voltage buffer is applied to an LDO implemented in a 0.35-mu m CMOS technology. The LDO operates at a 2-V supply, and the regulated voltage is 1.8 V. The maximum output current is 100 mA. The measured quiescent current is about 4 mu A. The load transient deviation of the regulated voltage is small. The proposed voltage buffer can effectively reduce the transient voltage spikes.