A Design Methodology for an Integrated CMOS Instrumentation Amplifier for Bioespectroscopy Applications

A design methodology for an integrated CMOS Current Feedback Instrumentation Amplifier (CFIA) intended for bioespectroscopy measurement is presented in this paper. This methodology takes into account key design aspects such as measurement probe geometry, noise and gain requirements, CMRR, PSRR and operation region considerations (g(m)/I-D analysis) of critical transistors of the amplifier to perform its sizing. Following this methodology, a differential output CFIA was designed in a 0.18- mu m CMOS process technology, achieving post-layout simulation results of CMRR averaging 100 dB, bandwidth of 2 MHz, power consumption of 634 mu W and base noise level lower than 16 mu V-rms for a differential gain goal of 50 V/V. This results make the designed circuit suitable for bioimpedance applications.