Group-Chopping: An 8-Channel, 0.04% Gain Mismatch, 2.1 µW 0.017 mm2 Instrumentation Amplifier for Bio-Potential Recording

An 8-channel AFE with a group-chopping instrumentation amplifier (GCIA) is proposed for bio-potential recording applications. The group-chopping technique cascades chopper switches to progressively swap channels and dynamically removes gain mismatch among all channels. An 8-phase non-overlapping clocking scheme is developed and achieves excellent between-channel gain mismatch characteristics. The dynamic offsets among all channels are mitigated by the GCIA as well. The GCIA is the first work that minimizes the gain mismatch across more than two channels. With the help of the group-chopping, combined with an area-efficient open-loop structure, the GCIA shows <0.04% between-channel gain mismatch, the lowest mismatch reported to date. The chip is fabricated in 0.18µm 1P6M CMOS, occupies only 0.017 mm²/Ch., consumes 2.1 μW/Ch. under 0.5 V supply and achieves an NEF of 2.1.