A Wearable 8-Channel Active-Electrode EEG/ETI Acquisition System for Body Area Networks Jiawei Xu, Srinjoy Mitra, Akinori Matsumoto, Shrishail Patki, Chris V an

Abstract

This paper describes an 8-channel gel-free EEG/elec- trode-tissue impedance (ETI ) acquisition system, cons isting of nine active electrodes (AEs) and one back-end (BE) analog signal processor. The AEs amplify the weak EEG signals, while their low output impedance suppresses cable-motion a rtifacts and 50/60 Hz mains interference. A common-mode feed-forward (CMFF) scheme boosts the CMRR of the AE pairs by 25 dB. The BE post-processes and digitizes the anal og outputs of the AEs, it also can con figure them via a single-wire pulse width modulation (PWM) protocol. Together, the AEs and BE are capable of recording 8-channel EEG and ETI signals. With EEG r e c o r d i n ge n a b l e d ,E T I so fu pt o6 0kΩ can be measured, which increases to 550 k Ω when EEG recording is disabled. Each EEG channel has a 1.2 G Ω input impedance ( at 20 Hz), 1.75 µVrms (0.5–100 Hz) input-referred noise, 84 dB CMRR and ±250 mV electrode offset rejection capability. The EEG acquisition system was implemented in a standard 0.18 µm CMOS process, and dissipates less than 700 µW from a 1.8 V supply.