A Fully Integrated Analog Front End for Biopotential Signal Sensing

A low-power fully-integrated analog front end for biopotential sensors is proposed. The signal conditioning circuitry features an integrating sampler and a digital-assisted electrode offset-cancellation loop. The chip is fabricated in a standard 0.18-mu m CMOS process. The supply voltage is 1.2 V and the quiescent current is 7.7 mu A. Measurement results show that the analog front end achieves an in-band gain of 58 dB, a noise spectrum density of 46nV/root Hz and can tolerate +/- 60 mV electrode offset. The THD is below 1% with a 2mV(pp) input. The analog signal is converted to digital code at 5kS/s by a 12-bit SAR ADC with 63.2 dB SNDR. The prototype IC is experimented with capturing ECG on human beings.