A 20.3μW 1.9GΩ Input Impedance Capacitively-Coupled Chopper-Stabilized Amplifier for Bio-Potential Readout

作者：Y. N. Zhou, Shuang Song, Yu Zheng, Tian Yang, Mengyu Li, Yipeng Cao, Feijun Zheng, Kai Huang, Zhichao Tan, Menglian Zhao · 发表于：IEEE Transactions on Circuits and Systems I Regular Papers · 年份：2024 · DOI：10.1109/tcsi.2024.3351872 · 被引用次数：12 · 研究领域：Ferroelectric and Negative Capacitance Devices、Advanced Memory and Neural Computing、Energy Harvesting in Wireless Networks

This paper presents a low-power chopper-stabilized capacitively-coupled frontend amplifier with auxiliary-path-based input impedance ( Z$_{\mathbf{in}}$) boosting. In order to achieve a high Z$_{\mathbf{in}}$, a low noise and a small chip area, techniques on both system level and circuit level are implemented. On the system level, small capacitors ( C$_{\mathbf{in}}$$=$0.5 pF, C$_{\mathbf{fb}}$$=$25 fF) are used with a biased pseudo-resistor ( R$=$2.5 G$\Omega $) fed back to an amplifier internal node. As a result, a high achievable Z$_{\mathbf{in}}$and low high-pass corner frequency are achieved. On the circuit level, an input capacitance shielded current feedback (CSCF) topology achieving effective 10 fF C$_{\mathbf{amp}}$is proposed as the core of the capacitive feedback amplifier in order not to increase the input noise. Moreover, the design space of auxiliary-path-based boosting is explored to obtain the optimal value of buffer bandwidth and auxiliary capacitor size to save power. The amplifier and its Z$_{\mathbf{in}}$boosting circuit are implemented in a standard 55 nm CMOS process and characterized experimentally. Measurement results show that the proposed amplifier provides an input noise density of 50 nV/$\surd$Hz, and an integrated noise of 0.85$\mu$V$_{\mathbf{rms}}$in 200 Hz band. The Z$_{\mathbf{in}}$is boosted to 1.92 G$\Omega $at DC and 1.02 G$\Omega $at 50 Hz with only 1.0$\mu$A in each auxiliary path buffer. The amplifier also archives 77 dB CMRR and 76 dB P...