A capacitively-coupled biomedical instrumentation amplifier employing chopping and auto-zeroing
This paper presents a low power high precision instrumentation amplifier (IA) for biomedical electronics such as EEG, ECG and neural recording. By using capacitively-coupled topology, wide input common-mode range and low power consumption is achieved. Chopping and auto-zeroing techniques are employed simultaneously to alleviate their own side-effects. A DC cancellation loop is used to suppress electrode offset. In addition, adverse effect of parasitic capacitances of input transistors is analyzed and alleviated. Improved switched-capacitor (SC) CMFB circuits are proposed to mitigate capacitance load effect. This IA is implemented in SMIC 0.18μm CMOS process. -3dB bandwidth of the IA can be set as 1 kHz or 10 kHz to fit different applications like EEG or neural recording. Simulation results show that it achieves equivalent input noise power spectrum density (PSD) of 42nV/√Hz, a noise efficiency factor (NEF) of 3.1 and CMRR of 128dB. It consumes 3.7μA from a 1V supply.