An Instrumentation Amplifier with High-Flexibility, High-CMRR and Low-Power Consumption for Electrical Impedance Tomography Applications

This paper presents a high-flexibility, high-CMRR instrumentation amplifier (IA) suitable for electrical impedance tomography (EIT) applications. It utilizes symmetric tunable pseudo-resistors to form a high-pass filter (HPF) at the amplifier’s front-end. The IA is highly flexible as it supports two distinct modes in tuning its bandpass corners. Due to the improved use of fully symmetrical drain networks and high output impedance source networks of the current-feedback instrumentation amplifier (CFIA)’s input stage, the IA circuit achieves a high common-mode rejection ratio (CMRR) of more than 90 dB at 1.5 MHz. The proposed IA has been simulated using a 180-nm CMOS process with a total input integrated noise within the 1 kHz – 2.356 MHz bandwidth below 20 μV<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf>. The entire circuit consumes 1.233 mW with a 3.3-V supply and occupies 0.146 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>.