A 0.12µV_rms input noise 4.14GΩ input impedance chopper and auto-zero instrumentation amplifier for EEG recording front ends

Abstract

This paper proposes a directly coupled instrumentation amplifier (IA) for EEG signal acquisition. By integrating both chopping and auto-zeroing (AZ) techniques, an offset and 1/f noise control loop (OFC) structure is proposed. Furthermore, a Capacitive Impedance Boost Loop (CIBL) configuration is presented to augment the input impedance within the EEG frequency band. Using the Common-Mode Biasing Circuit, the common mode rejection ratio (CMRR) of the circuit is improved. Fabricated in a 180-nm CMOS process, the prototype IA has the input-referred noise of 0.12µV_rms from 0.01Hz to 100Hz. The proposed IA achieves high-input impedances of 4.14GΩ at 20Hz, and CMRR of 133.1dB at 70Hz.