IEEE Trans Biomed Circuits Syst. 2019 Oct;13(5):918-926. doi: 10.1109/TBCAS.2019.2924416. Epub 2019 Jun 24.
High input impedance, low noise, high common mode rejection ratio (CMRR), and ultralow power are the most important performance indicators in the design of analog front end (AFE) for wearable biomedical sensors. This paper presents a fully differential difference amplifier based AFE that employs dc-coupled input stage to increase the input impedance and improve CMRR. A parasitic capacitor reuse technique is proposed to improve the noise/area efficiency and CMRR. An on-body dc bias scheme is introduced to deal with the input dc offset. Implemented in 0.35 μm CMOS process with an area of 0.405 mm, the proposed AFE consumes 0.9 μW at 1.8 V and shows excellent noise effective factor of 2.55, and CMRR of 76 dB. Experiment shows the proposed AFE not only picks up clean ECG signal with electrodes placed as close as 2 cm under both resting and walking conditions, but also obtain the distinct α-wave after eye blink from EEG recording.
高输入阻抗、低噪声、高共模抑制比 (CMRR) 和超低功耗是可穿戴生物医学传感器模拟前端 (AFE) 设计中最重要的性能指标。本文提出了一种基于全差分差分放大器的 AFE，采用直流耦合输入级来提高输入阻抗并改善 CMRR。提出了一种寄生电容复用技术来提高噪声/面积效率和 CMRR。引入了一种体上直流偏置方案来处理输入直流失调。该 AFE 采用 0.35μm CMOS 工艺实现，面积为 0.405mm，在 1.8V 下仅消耗 0.9μW，具有出色的噪声有效因子 2.55 和 CMRR 76dB。实验表明，所提出的 AFE 不仅可以在休息和行走条件下将电极放置在距离 2cm 以内的情况下采集到干净的 ECG 信号，而且还可以从 EEG 记录中获得眨眼后的明显α波。
