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 mu A 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.