A chopper capacitive feedback instrumentation amplifier with input impedance boosting technique

A chopper capacitive feedback instrumentation amplifier (CCFIA) with proposed input impedance boosting technique is presented. Using a negative capacitance circuit, the proposed boosting technique achieves higher input impedance across frequency when compared to traditional approaches without injecting current back to a biopotential electrode attached to human body. Moreover, boosting the input impedance is at no expense of the input referred noise of the CCFIA. A ripple reduction loop (RRL) is employed for suppressing the output chopping ripples. Also, a DC servo loop is designed for filtering out the electrode DC offset. Simulation results, using UMC 65 nm CMOS technology, demonstrate that the proposed input impedance boosting technique achieves much higher than 2 GO input impedance. In addition, the maximum input referred ripple is less than 1 μV. The CCFIA can tolerate up to 20 mV of electrode DC offset. The overall CCFIA achieves an input referred noise PSD equals to 35 nV/√Hz and bandwidth equals to 450 Hz with supply voltage equals to 1.2 V.