A current-feedback instrumentation amplifier with a gain error reduction loop and 0.06% untrimmed gain error

Current-feedback instrumentation amplifiers (CFIAs) have significant advantages over the classic three-opamp topology: better power efficiency higher CMRR and rail-sensing capability. Their main disadvantage, however, is their limited gain accuracy, which is determined by the mismatch of two transconduc tors. Using resistor-degenerated differential pairs, 0.1% gain error and improved linearity have been achieved. However, this incurs either increased noise or increased power. This paper describes a chopper CFIA that employs a contin uous-time (CT) gain error reduction loop (GERL) without incurring a noise penalty. Without trimming, it achieves a gain error of less than 0.06% and a max imum gain drift of 6ppm/°C in a power efficient manner (NEF=11.2).