A Capacitively-Coupled Biomedical Instrumentati on Amplifier with Novel Ripple Reduction Loop

This paper describes a low-power precision capacitively-coupled chopper instrumentation amplifier (CCIA) to amplify the bio-potential signals. To reduce the offset and 1/f noise, chopping is employed. And the resulting ripple caused by the up-modulated offset and 1/f noise is suppressed by a proposed ripple reduction loop with chopped Ping-Pong auto-zeroing topology. With the proposed RRL, the chopping ripple at the output stage of the CCIA is attenuated about 40 dB. A DC servo loop (DSL) with a large time constant is employed to suppress electrode offset and a positive feedback loop (PFL) is employed to boost the input impedance. The CCIA is implemented in SMIC 0.18 μm CMOS process. To fit applications like EEG or ECG signals, -3 dB bandwidth is set as 1 kHz. Simulation results show that it achieves an equivalent input noise power spectrum density (PSD) of \rmnV/\sqrt \rmHz , a noise efficiency factor (NEF) of 2.1, CMRR of 105 dB and a supply current of 2.8 μA at a 1 V supply voltage.