A low power high CMRR CMOS instrumentation amplifier for Bio-impedance Spectroscopy

In this paper, a high Common-Mode Rejection Ratio (CMRR) and low power CMOS Instrumentation Amplifier (IA) for use in Bio-impedance Spectroscopy (BIS) is presented. It consists of a complementary Differential Voltage - Current Conveyor (DVCC) that provides the common-mode signal rejection and high input impedance, a Folded - Cascode Operational Transconductance Amplifier (FC-OTA) that serves as a gain stage, and a high pass filter built using a PMOS pseudo-resistor. The IA was implemented using TSMC 0.35µm 2P4M Polycide Technology and simulations were carried out using HSPICE. The designed IA features a CMRR of 120.2dB, a differential input impedance of 102.3MΩ, and a common-mode input impedance of 41.3MΩ both at 50kHz, while dissipating an average static power of 290µW.