High Input Impedance Low-Noise CMOS Analog Frontend IC for Wearable Electrocardiogram Monitoring

摘要

This brief presents a CMOS analog frontend (AFE) IC with high input impedance low input-referred noise, which for wearable electrocardiogram monitoring. The IC has three main parts, pseudo-differential chopper-stabilized instrumentation amplifier, switched capacitor filter, and low-power continuous-time Sigma Delta modulator. The pseudo-differential structure with chopper stabilization improves the input impedance, input-referred noise and chip area. Notably, we propose a new type of negative capacitor circuit to further boost the input impedance. Furthermore, the auto-zero technique is applied to the ripple reduction loop for suppressing the second harmonic ripple and maintain operation throughout the loop cycle. A dc servo loop suppresses the electrode dc offset. In 0.18 mu m CMOS process, the proposed AFE IC occupies an active area of 0.99 mm(2), consumes 5.8/46.6 mu A from a 1.8 V supply, and achieves an input impedance above 2 G Omega, a CMRR of 102 dB and a PSRR of 72 dB.