A Biopotential Amplifier With Enhanced Common-Mode Interference Resistance for Two-Electrode ECG Acquisition

This paper presents a biopotential amplifier designed for Electrocardiogram (ECG) recording in motion states, featuring enhanced common mode interference (CMI) suppression. The amplifier incorporates a common-mode suppression module based on steady-state convergence (SSC), utilizing only nine MOSFETs, two capacitors, two pseudo resistances, and a unity gain buffer. By implementing common mode charge detection and compensation, the SSC circuit effectively mitigates CMI of 20 VPP. To further improve the common-mode rejection ratio (CMRR), a common-mode replication technique is employed. A prototype has been fabricated using a 0.18 μm CMOS process with a 1.8 V supply, demonstrating a low power consumption of 16.7 μW. Measurement results indicate that the 20 VPPCMI is suppressed to below 200 mVPP, achieving a CMI suppression ratio greater than 100. Additionally, the amplifier exhibits an input-referred noise (IRN) of 1.26 μVrms, with TCMRR and power supply rejection ratio (PSRR) at 50 Hz reaching 91 dB and 83 dB, respectively.