Design and Evaluation of a Chopper-Stabilized Current-Feedback Instrumentation Amplifier for EEG and Biopotential Acquisition

Abstract

This paper presents a low-power chopperstabilized CMOS amplifier for EEG signal acquisition related to voluntary motor control in the primary motor cortex. Designed in a $0.18 \mu \mathrm{~m}$ CMOS process, the amplifier employs an ACcoupled chopper core to suppress 1/f noise, with tunable MOS capacitors and pseudo-resistors enabling programmable bandwidth. A positive-feedback impedance boosting loop (IBL) enhances input impedance and CMRR, ensuring accurate recording of low-amplitude neural signals. The circuit includes input protection and a band-pass filter tuned to the $\mathbf{1 4 - 3 0 ~ H z}$ beta rhythm. Simulation results demonstrate a mid-band gain of $\mathbf{7 2 ~ d B}$, a CMRR of $\mathbf{1 1 8 ~ d B}$, and an input-referred noise of $\mathbf{2 0 0} \mathrm{nV} / \sqrt{ } \mathrm{Hz}$ at $\mathbf{3 0 ~ H z}$, while consuming only $0.95 \mu \mathrm{~W}$ from a $\pm 0.9 \mathrm{~V}$ supply. With a noise-efficiency factor of 2.1, the design achieves an excellent balance between low noise, power, and area, making it suitable for compact, high-density EEG and neural acquisition systems.