33.8 A Two-Electrode Bio-Impedance Readout IC with Complex-Domain Noise-Correlated Baseline Cancellation Supporting Sinusoidal Excitation

As the demand for daily monitoring of physiological signals increases, the trend towards minimizing the size of devices through a two-electrode configuration has emerged as a new standard for wearable impedance monitoring. However, the two-electrode impedance measurement configuration suffers from its large baseline, further increased by the electrode impedance and the amplified noise of the current generator (CG). These challenges have been addressed by real-domain noise-correlated baseline cancellation (BC) techniques [1–3] (Fig. 33.8.1 (top)). It performs baseline subtraction using an IDAC, whose current is correlated with the current from the CG, at the front-end current-balancing instrumentation amplifier (CBIA). This method operates well with square-wave signals of the CG, and demonstrates strong noise-cancellation capabilities, especially in resistive BioZ.