A Capacitively-Coupled Chopper Instrumentation Amplifier for Implantable Bridge Sensor Systems

This paper presents an energy and area efficient capacitively-coupled chopper instrumentation amplifier (CCIA) dedicated to implantable bridge sensor systems. Chopper stabilization is employed to decrease its offset and 1/f noise and the resulting ripple due to the up-modulated offset and 1/f noise is suppressed by a switched-capacitor ripple reduction loop. The gain of the instrumentation amplifier is defined by a programmable capacitive feedback network with a gain range from 40 V/V to 116 V/V, which is suitable for use with bridge sensors having different output voltages. The proposed CCIA has been fabricated in a standard 0.18 mu m CMOS process. It achieves an input noise of 88.2 nV/root Hz, a worst-case input offset of 5 mu V, and an output ripple of less than 185 mu V. The CCIA occupies only 0.17 mm(2) chip area and draws 3.3 mu A current from a 1.2 V supply.