This paper proposes a cardiac electrogram acquisition and stimulation integrated circuit (IC) for single-chamber leadless pacemaker applications. The proposed IC features self-determining pacing by acquiring an intracardiac electrogram without an external digital signal processor (DSP). A novel current-feedback instrumentation amplifier (CFIA) is proposed to achieve high noise-power efficiency and high input impedance. In this proposed CFIA, the current-reused cascode differential-difference input stage and class-AB biasing stage are merged. The electrocardiogram (ECG) sensing channel, equipped with a 60-Hz notch filter to relieve powerline interference (PLI), achieves a power supply rejection ratio (PSRR) of 80 dB, a common-mode rejection ratio (CMRR) of 174 dB, and an input-referred noise of $3.47~\mu $ VRMS, in a 350 Hz bandwidth. The ECG acquisition and cardiac pacing functionality of the IC are evaluated in a swine’s right ventricle via a 4-electrode catheter.
