A Leakage-Attenuated Auto-Zeroing High-Pass Filter Using Switch Voltage Regulation

Abstract

This paper presents leakage-attenuated feedback (LAF) auto-zeroing high-pass filter (AZHPF) for various analog front-end applications. AZHPF is widely used to cancel DC offset. However, AZHPF suffers from leakage induced voltage decay during auto-zeroing phase. This leads to large offset error and performance degradation particularly at low operation frequency. To overcome this limitation, LAF is proposed. As a result, the proposed LAF AZHPF achieves improved offset cancellation. Simulation results verify the effectiveness of the proposed approach, making the proposed AZHPF suitable for low-frequency precision applications. In this proposed design, an error amplifier is used to regulate the voltage across the switches connected to the sampling capacitor. By maintaining equal voltage levels at both switch nodes, the stored offset voltage is preserved over time without increasing the sampling capacitance. Simulation results demonstrate the proposed design successfully achieves lower offset error than the conventional design over wide range from 10 mHz to 1 kHz. In particular, the proposed approach validates its effectiveness as a general solution for leakage current prevention at low frequency in auto-zeroing circuits.