Capacitor-Less Low-Dropout (LDO) Regulator With 99.99% Current Efficiency Using Active Feedforward and Reverse Nested Miller Compensations

In this paper, an output capacitor-less low-dropout (LDO) regulator with 99.99% current efficiency using active feedforward compensation (AFFC) and reverse nested Miller compensation (RNMC) is implemented. To increase the current efficiency, low quiescent current less than 10 μA is used. The stability problem arising from the low bias current is overcome by applying two kinds of compensation methods. By drawing the pole-zero plot using the open-loop transfer function obtained by the small-signal modeling, the stability of the proposed LDO is guaranteed to be less than 70 mA. By using the proposed compensation methods, two zeros of the right-half plane (RHP) can be placed in the left-half plane (LHP) to prevent lagging and reduce the on-chip compensation capacitor. The current efficiency of the proposed LDO is 99.99% at the load current of 70 mA.