A 1.8-V 770-nW biopotential acquistion system for portable applications

In this paper, an ultra-low power biopotential acquisition system is presented. The proposed system contains a tunable band-pass amplifier, a VGA with strong capacitive driving capability and a successive approximation ADC. To make the gain and bandwidth programmable, a T-switch with huge cut-off resistor is utilized to eliminate the effect of low frequency doublets. An improved low kick-back noise low offset latch brings a significant power reduction to the SAR ADC. The design was implemented in 0.18 ¿ m CMOS process and consumes 770 nW from a 1.8-V single supply. The analog front-end achieves a 193 Hz to 407 Hz programmable bandwidth, 41.5 dB to 62 dB tunable gain, 3.7 ¿ Vrms (0.025 Hz~200 Hz) input referred noise, noise efficiency figure (NEF) of 3.1. The SAR ADC achieves 11.7-bit ENOB.