A 0.5-V 1.3- Analog Front-End CMOS Circuit

This brief presents a low-power analog acquisition front-end circuit for a Wireless Body Area Network. This front-end system mainly consists of three parts, namely, chopped capacitively coupled instrumentation amplifier (CCIA), switched capacitor filter (SC-filter), and successive-approximation analog-to-digital converter. In order to reduce the power consumption, the supply voltage is scaled to 0.5 V, and all analog building blocks are biased in the subthreshold region. The chopper-stabilized technique is introduced to eliminate the 1/f noise, and a dc-servo loop is employed in the CCIA to suppress the electrode offset. A low-power second-order SC-filter is employed to eliminate the spikes produced by the CCIA, which also realizes a tunable gain to satisfy the specification. This low-power analog front-end circuit has been fabricated in a 0.18-μW CMOS process. It occupies 1 mm2and consumes a minimal 1.3 μW at 0.5 V. It achieves a bandwidth of 0.5-250 Hz, a CMRR of 95 dB, and an input impedance of 48 MΩ, respectively.