A 1V 3.5 μW Bio-AFE With Chopper-Capacitor-Chopper Integrator-Based DSL and Low Power GM-C Filter

This brief presents a low-noise, low-power bio-signal acquisition analog front-end (Bio-AFE). It mainly includes a capacitively coupled chopper-stabilized instrumentation amplifier (CCIA), a programmable gain amplifier (PGA), a low-pass filter (LPF), and a successive approximation analog to digital converter (SAR ADC). A chopper-capacitor-chopper integrator based DC servo loop (C 3 IB-DSL) to suppress the electrode DC offset (EDO) with low noise, low process-voltage-temperature (PVT) sensitivity is proposed. Besides, a low power GM-C filter of which the input linear range is extended via inverse hyperbolic tangent pre-distortion circuit is proposed to filter out the spikes, ripples, and high frequency noise in front end. A capacitive feedback PGA is employed to realize a tunable gain of the front end. And a low power SAR ADC is applied to quantify the acquired bio-signal. The proposed analog front end has been fabricated in a 0.18\boldsymbol{\mu }\text{m} CMOS process with an area of 0.57mm 2 , consuming 3.5~\boldsymbol{\mu }\text{A} from a 1V supply voltage. It achieves an integral noise from 0.5 to 100 Hz of 1.16\boldsymbol{\mu }\text{V}_{\mathrm{ rms}} , ±90mV EDO cancellation range, an ADC effective number of 9.06 bit, and the −59.6 dB total harmonic distortion (THD) of total AFE.