Abstract
A biopotential acquisition analog front-end (AFE) integrated circuit (IC) is presented. The biopotential AFE includes a capacitively coupled chopper instrumentation amplifier (CCIA) to achieve low input referred noise (IRN) and to block unwanted DC potential signals. A DC servo loop (DSL) is designed to minimize the offset voltage in the chopper amplifier and low frequency respiration artifacts. An AC coupled ripple rejection loop (RRL) is employed to reduce ripple due to chopper stabilization. A capacitive impedance boosting loop (CIBL) is designed to enhance the input impedance and common mode rejection ratio (CMRR) without additional power consumption, even under an external electrode mismatch. The AFE IC consists of two-stage CCIA that include three compensation loops (DSL, RRL, and CIBL) at each CCIA stage. The biopotential AFE is fabricated using a 0.18 µm one polysilicon and six metal layers (1P6M) complementary metal oxide semiconductor (CMOS) process. The core chip size of the AFE without input/output (I/O) pads is 10.5 mm2. A fourth-order band-pass filter (BPF) with a pass-band in the band-width from 1 Hz to 100 Hz was integrated to attenuate unwanted signal and noise. The overall gain and band-width are reconfigurable by using programmable capacitors. The IRN is measured to be 0.94 µVRMS in the pass band. The maximum amplifying gain of the pass-band was measured as 71.9 dB. The CIBL enhances the CMRR from 57.9 dB to 67 dB at 60 Hz under electrode mismatch conditions.
Highlights
Human-computer interface applications have gained significant attention
Biopotential detection devices enable continuous monitoring of various physiological information from a user; the biopotential detection circuits can be utilized in fields like medical, entertainment, and sports fields [1,2]
Most biopotential circuits commonly suffer from degraded performance because of the flicker noise in the bio-signal band, offset due to process variation, skin-to-electrode offset, and motion artifact signals from different body and cable motions during signal recording
Summary
Human-computer interface applications have gained significant attention. Many major global companies have developed various individualized bio-signal measuring applications. Most biopotential circuits commonly suffer from degraded performance because of the flicker noise in the bio-signal band, offset due to process variation, skin-to-electrode offset, and motion artifact signals from different body and cable motions during signal recording. To effectively attenuate the unwanted components out of the biopotential signal band, a higher order high-pass filter (HPF) with a sub-Hz cut-off frequency is required. The presented AFE is designed to be fully integrated and is fabricated using a standard 0.18-μm complementary metal oxide semiconductor (CMOS) process
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