A >130-dB CMRR Capacitively Coupled Chopper Instrumentation Amplifier Employing Orthogonal Timing Mismatch Averaging for Biosignal Sensing

This paper presents a capacitively-coupled chopping instrumentation amplifier (CCIA) with orthogonal timing mismatch averaging (OTMA) technique for bio-signal sensing. OTMA employs additional pairs of choppers in input and feedback networks, to mitigate all the passive component mismatches through four orthogonal phases. OTMA substantially increases the common-mode rejection ratio (CMRR) without the need for complex correction loops or extra pathways. Designed in 130 nm CMOS technology, the proposed CCIA with OTMA draws 3.5 μA from a 1.8-V supply and exhibits 0.63 μVrms input-referred noise over 0.5-200 Hz. It achieves >130 dB CMRR with a compact chip area.