Analysis and design of a new COA-based current-mode instrumentation amplifier with robust performance against mismatches

In this paper, analysis and design of a new current-mode instrumentation amplifier (CMIA) circuit is presented. The proposed circuit employs two Current Operational Amplifiers (COA) as active building blocks, one resistor and two transistors operating as variable resistors to electronically control the differential-mode gain. The main feature of the proposed CMIA is that unlike most previously reported CMIAs, its CMRR has negligible sensitivity to mismatches. In addition, in the proposed circuit both active building blocks operate in negative feedback loop which results in an overall enhanced performance. SPICE simulation results using 0.18 μm TSMC CMOS parameters and supply voltage of ±0.9 V show a constant CMRR of about 51 dB regardless of mismatches and wide bandwidth ranging from 14.8 MHz to about 3 MHz for differential-mode gains between 3 and 18 dB, respectively.