A 0.8-μW and 74-dB High-Pass Sigma-Delta Modulator with OPAMP Sharing and Noise-Coupling Techniques for Biomedical Signal Acquisition

This work presents a third-order high-pass sigma-delta modulator (HPSDM) for biomedical signal acquisition. The operational amplifier (op-Amp) sharing and noise-coupling techniques are adopted to reduce the required quantity of op-Amps and add a noise-shaping order, which can achieve low power consumption and high resolution. A novel switched-capacitor architecture is proposed to suppress the increasing in-band noise and alleviate the circuit sensitivity to capacitor mismatch in the high-pass integrator. The proposed HPSDM was fabricated in a 0.18-μm standard CMOS process. Measurement results reveal that the proposed HPSDM has a signal-To-noise and distortion ratio (SNDR) of 75.26/74 dB in 200 Hz bandwidth and consumes 1.52/0.8 μW under 1.2/1 V supply voltage, which can achieve a peak Schreier Figure-of-Merit of 156.45/157.98 dB and a peak Walden FoM of 0.802/0.488 pJ/conv.