High linearity and large output swing sub-Hz pre-amplifier for portable biomedical applications

This paper presents a high-linearity and large output swing instrumentation amplifier for portable multichannel biomedical applications. It is composed of a fully differential two-stage CMOS amplifier in which a feedback provides stable signal gain that can be adjusted from 25 to 100 V/V. Additionally, a pseudo-resistive feedback combined with an appropriate input capacitive coupling provides a high-pass behavior, presenting a -3 dB cut-off frequency lower than 120 mHz. The amplifier is fully integrated in a 130 nm CMOS process, using only 0.1 mm² of silicon area, including large matched capacitor banks. Its power consumption is 31.3 μW under a 1.5 V supply. The pre-amplifier gain reaches less than 0.02 % of THD (total harmonic distortion) for an output swing of 2 Vpp in post-layout simulations. The total input-referred noise estimated from simulations is 1.93 μVrms inside the 0.5 Hz to 500 Hz frequency range.