A Low-Noise, Low-Power Amplifier With Current-Reused OTA for ECG Recordings

Abstract

This paper presents a low-power and low-noise capacitive-feedback amplifier with a current-reused OTA for ECG recordings. To improve the noise-power efficiency, the proposed OTA employs a current-reused architecture, which adopts an inverter-based differential input stage for low noise, and a class-AB output stage for large output range and high g_m/I efficiency. The driving branch of the class-AB output stage is merged into the input stage to realize current reuse and reduce power consumption further. Fabricated in a 0.35-μm CMOS process, the amplifier consumes 160 nA from a 2-V supply, while achieving an input-referred noise of 2.05 μV_rms, corresponding to a noise efficiency factor (NEF) of 2.26. The measured common-mode rejection ratio (CMRR) and power supply rejection ratio (PSRR) exceed 65 dB and 70 dB, respectively. The total harmonic distortion (THD) is less than 1% with a 15-mV_pp input at 20 Hz and the active area is 0.3 mm × 0.6 mm.