Analog Frontend for ECG/EMG Capacitive Electrodes

In this paper, a complete analog frontend for ECG/EMG signal acquisition through non-contact capacitive electrodes is designed. The main part of the analog signal acquisition chain is a low noise, low input bias current preamplifier, which was designed in both bootstrapped and transimpedance amplifier configurations. The preamplifier is followed by the cascade of active
$\boldsymbol{2^{\text{nd}}}$
order high-pass filter with a 20 dB gain and
$\boldsymbol{4^{\text{th}}}$
order active low-pass Sallen-Key filter using Butterworth approximation and 40 dB gain. The effects of coupling capacitance on system noise and gain-frequency response for both preamplifier topologies are investigated. The simulated input-referred noise, with a coupling capacitance value equal to 100 pF, for both preamplifier topologies has the value of 2.9
$\boldsymbol{\mu \mathrm{V}_{\text{RMS}}}$
. The gain-frequency response of bootstrapped preamplifier achieved greater resilience to variation of coupling capacitance value compared to transimpedance amplifier configuration, especially for lower values of coupling capacitance.