This work reports an ear-EEG acquisition system with dry-contact active electrodes for future wearable applications. Employing dedicated chopper buffer in the active electrodes, a prototype fabricated in a 0.18-µm CMOS demonstrates input impedance as large as 18GΩ@DC and 6.7GΩ@50Hz, and 3.03fA/vHz input current noise, and a total input-referred noise (IRN) of 0.67µV rms  in 0.5–100Hz bandwidth. System's CMRR in combination with active electrodes is higher than 100dB@DC. Under large source impedance imbalance of 1MΩ, a 78-dB@50Hz CMRR is still obtained. To validate the system's ability to record EEG, an auditory stead-state response was measured, showing same SNR with wet electrodes and a commercial EEG amplifier.
['Xiong Zhou', 'Qiang Li', 'Soren Kilsgaard', 'Farshad Moradi', 'Simon Lind Kappel', 'Preben Kidmose']
A wearable ear-EEG recording system based on dry-contact active electrodes