Low quiescent current LDO with FVF-based PSRR enhanced circuit for EEG recording wearable devices

Abstract

This paper presents a low quiescent current low-dropout regulator (LDO) with an auxiliary amplifier, flipped voltage follower (FVF)-based power supply rejection ratio enhanced circuit (FBPEC) for electroencephalogram (EEG) recording devices. The FBPEC comprises a FVF filter, current mirror, and common-source amplifier. The FBPEC exploits the characteristics of FVF filter to reduce the current consumption and increase the gain at specific frequencies. The small-signal equivalent circuit reveals the dominant pole of the FBPEC, which is affected by the output impedance and load capacitance of the common-source amplifier. The proposed LDO is designed using a 0.18 μm CMOS process and has improved power supply rejection ratio (PSRR) up to 18 dB at frequencies above 10 kHz compared to the general LDO. The proposed LDO has a low no-load quiescent current 648 nA and a good figure-of-merit score compared to those of previous works, proving that the proposed circuit is an effective solution for use in wearable EEG recording devices.