A Complementary Pseudo-Resistor with Leakage Current Self-Compensation for Biopotential Amplifiers

Conventional pseudo-resistors used in AC-coupled biopotential amplifiers suffer from intrinsic and photo-induced leakage currents, which may saturate the amplifier and induce an input-amplitude-dependent DC drift at the amplifier output. To mitigate these issues, this paper presents a new complementary pseudo-resistor with a leakage current self-compensation mechanism. As proof of concept, a capacitive feedback biopotential amplifier using the proposed pseudo-resistor is designed in the DB HiTek 180nm CMOS process. In the measurement, it achieves enhanced robustness against both input-amplitude-dependent DC drift and light exposure, compared to the amplifier using the conventional pseudo-resistor. It also demonstrates high signal fidelity during in vitro tests using pre-recorded neural signals.