A biopotential acquisition analog front-end (AFE) integrated circuit (IC) is\npresented. The biopotential AFE includes a capacitively coupled chopper instrumentation\namplifier (CCIA) to achieve low input referred noise (IRN) and to block unwanted DC\npotential signals. A DC servo loop (DSL) is designed to minimize the offset voltage in the\nchopper amplifier and low frequency respiration artifacts. An AC coupled ripple rejection\nloop (RRL) is employed to reduce ripple due to chopper stabilization. A capacitive\nimpedance boosting loop (CIBL) is designed to enhance the input impedance and common\nmode rejection ratio (CMRR) without additional power consumption, even under an external\nelectrode mismatch. The AFE IC consists of two-stage CCIA that include three\ncompensation loops (DSL, RRL, and CIBL) at each CCIA stage. The biopotential AFE is\nfabricated using a 0.18 �¼m one polysilicon and six metal layers (1P6M) complementary\nmetal oxide semiconductor (CMOS) process. The core chip size of the AFE without\ninput/output (I/O) pads is 10.5 mm2. A fourth-order band-pass filter (BPF) with a pass-band\nin the band-width from 1 Hz to 100 Hz was integrated to attenuate unwanted signal and\nnoise. The overall gain and band-width are reconfigurable by using programmable\ncapacitors. The IRN is measured to be 0.94 �¼VRMS in the pass band. The maximum\namplifying gain of the pass-band was measured as 71.9 dB. The CIBL enhances the CMRR\nfrom 57.9 dB to 67 dB at 60 Hz under electrode mismatch conditions.
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