An 8-channel chopper-stabilized analog front-end amplifier for EEG acquisition in 65-nm CMOS

An 8-channel chopper-stabilized analog front-end amplifier (AFEA) is designed in 65-nm CMOS for continuous EEG signal acquisition. The AFEA is composed of eight capacitively coupled chopper instrumentation amplifiers (CCCIAs) with chopper-stabilized circuits and band-pass filters, a multiplexed transconductor, and a transimpedance amplifier. The CCCIA employs an inverter-based folded-cascode amplifier (IBFC) to achieve a better noise-to-power tradeoff and a high gain under 1 V power supply, a DC servo loop to suppress electrode offset and provide a low high-pass corner, a low power ripple reduction loop to suppress chopping ripple, and a positive feedback loop to boost its input impedance. The fabricated AFEA has 59.1/69.8/78 dB programmable gain and 0.81 μVrms input-referred noise in a bandwidth of 0.5-100 Hz. The measured power consumption of a single CCCIA is 0.87 μW. The proposed CCCIA has a lower NEF of 2.97 than other CCCIA for EEG acquisition.