Design of an Adaptively Biased Low-Dropout Regulator With a Current Reusing Current-Mode OTA Using an Intuitive Analysis Method

An adaptively biased low-dropout regulator (AB-LDO) with current mirror buffer has been proposed in previous literatures, which only solves a few of the specific problems of AB-LDO without additional synthetical analysis of the various performances. Based on the analysis, it is found that enhancing the current efficiency of operational transconductance amplifier (OTA) is a key factor to improve the performances of AB-LDO. A current reusing current-mode OTA (CRCM-OTA) with high current efficiency is proposed to apply to AB-LDO. Compared with the traditional AB-LDO, it can achieve an obvious improvement of AB-LDO performances including the current efficiency of AB-LDO, loop gain, and loop bandwidth without increasing the area and power consumption. This article also adopts an intuitive method different from the previous works to analyze the whole loop. The AB-LDO using an advanced CRCM-OTA was fabricated in SMIC 0.18 mu m CMOS process, which has a transient undershoot of 26.25 mV with an output capacitor of 1 mu F for a load step of 0-50 mA with edge time of 10 ns and realizes a performance figure of merit (FoM) value of 13.65 ps.