A 1.9 µW 127 n V/ √Hz Bio Chopper Amplifier Using a Noise-Efficient Common Mode Cancelation Loop

Electrical neural stimulation (ENS) is widely used for implantable applications to convey information to nervous tissue. However, ENS will generate large common (CM) artifacts at the electrode tissue, leading to saturate the traditional biopotential amplifier. This paper presents a low power low noise bio chopper amplifier (BiCA) for the recording of biopotential signals. The proposed noise-efficient common mode cancelation (N-CMC) loop helps BiCA handle 650 mVpp CM artifact and avoid its noise contribution. Moreover, N-CMC helps BiCA improving the signal-noise-ratio from 12.8 to 49 dB. Beside, the proposed BiCA also uses a DC servo loop (DSL) and a ripple suppression loop (RSL) to address the electrode offset (EOS) and intenal offset (VOS), respectively. The proposed BiCA implemented in a 180 nm CMOS technology occupies only 0.11 mm2, The simulation results of the BiCA show an input referred noise of 2.73 µVrms. A common-mode rejection ratio (CMRR) and a power rejection ratio (PSRR) are 133 and 129 dB, respectively, at 50 Hz. The total current consumption of BiCA is 1.9 µA from a 1 V supply.