A 160μW 8-Channel Active Electrode System for EEG Monitoring
J Xu (TU Delft - Electronic Instrumentation)
RF Yazicioglu (IMEC)
B. Grundlehner (Stichting IMEC Nederland)
Pieter Harpe (Eindhoven University of Technology)
K.A.A. Makinwa (TU Delft - Electronic Instrumentation)
Chris van Hoof (IMEC)
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Abstract
This paper presents an active electrode system for gel-free biopotential EEG signal acquisition. The system consists of front-end chopper amplifiers and a back-end common-mode feedback (CMFB) circuit. The front-end AC-coupled chopper amplifier employs input impedance boosting and digitally-assisted
offset trimming. The former increases the input impedance of the active electrode to 2 G at 1 Hz and the latter limits the chopping induced output ripple and residual offset to 2 mV and 20 mV respectively. Thanks to chopper stabilization, the active electrode achieves 0.8 μVrms (0.5-100 Hz) input referred noise. The use of a back-end CMFB circuit further improves the CMRR of the active electrode readout to 82 dB at 50 Hz. Both front-end and back-end
circuits are implemented in a 0.18 μm CMOS process and the total current consumption of an 8-channel readout system is 88 μA from 1.8 V supply. EEG measurements using the proposed active electrode system demonstrate its benefits compared to passive electrode systems, namely reduced sensitivity to cable motion artifacts and mains interference.