CMOS Low-Voltage Indirect Current Feedback Instrumentation Amplifiers With Improved Performance

Indirect current feedback (ICF) is a very common operation principle used in the design of CMOS instrumentation amplifiers (IA). The input and output transconductors required in an ICF IA usually consist on resistive-degenerated simple differential pairs. In this contribution conventional source-follower (SF) structures used in IA transconductors are replaced by flipped-voltage-follower (FVF) and super-source-follower (SSF) cells, respectively. As a result, the overall performance and efficiency of the IA is enhanced with a minimum cost. The principle of operation governing CMRR is also analyzed and its behavior is confirmed by means of extensive simulations. A single-stage IA with a fixed voltage gain equal to 10 V/V has been designed in $0.35-\boldsymbol{\mu} \mathbf{m}$ standard CMOS technology to operate with 1.8 V supply. Simulation results show improved metrics in terms of voltage gain accuracy, while the overall performance of the IA is comparable to other contributions in the literature.