A high-pass sigma–delta modulator (HPSDM) that uses operational amplifier (op-amp) sharing and programmable feed-forward coefficients is presented for an electrocardiography (ECG) signal detection system. Op-amp sharing is used to reduce the quantity of amplifiers because they dominate the entire power consumption of the HPSDM. Moreover, the amplitude of the ECG varies from person to person; hence, programmable feed-forward coefficients are used to adjust the dynamic range of HPSDM to obtain high resolution across users. This technique is implemented using the 0.18 μm standard CMOS process. Measurement results reveal that the proposed HPSDM has a signal-to-noise and distortion (SNDR) of 54.5 dB and a power of 2.25 μW under a 1.2 V supply voltage to achieve the figure of merit of 12.96 pJ/conv. In terms of other settings, the proposed HPSDM has an SNDR of 64.8 dB and a power of 5.2 μW under a 1.8 V supply voltage to achieve the figure of merit of 9.15 pJ/conv. Both modes extend the dynamic range of 12 dB according to the programmable feed-forward coefficients.