Key result
Low-power capacitive-feedback amplifier with current-reused OTA achieves 2.05 μVrms input-referred noise.
Why the study?
Low-noise and low-power amplifiers with improved noise-power efficiency are needed for ECG recordings.
The proposed current-reused OTA architecture provides a highly efficient, low-noise, and low-power amplifier suitable for ECG recordings.
May enable prolonged wearable ECG monitoring; leaves open clinical validation of the amplifier in patient devices.
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 gm/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 μVrms, 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-mVpp input at 20 Hz and the active area is 0.3 mm × 0.6 mm.
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Zhang et al. (2018) studied ECG recordings. Low-power and low-noise capacitive-feedback amplifier with a current-reused OTA was evaluated on Input-referred noise, noise efficiency factor (NEF), CMRR, PSRR, and THD. A low-power capacitive-feedback amplifier with a current-reused OTA achieved an input-referred noise of 2.05 μVrms and a noise efficiency factor of 2.26 while consuming 160 nA.
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