A 45-V Auto-Zero-Stabilized Chopper Instrumentation Amplifier With 1.8- μ V Offset, 33.5- μ V Ripple, and 42-V Common-Mode Input Range

This letter presents a 45V high-precision current-feedback instrumentation amplifier (CFIA) that combines both chopping and auto-zeroing (AZ) to achieve 1.8- $\mu $ V input offset (10 samples) and 33.5- $\mu $ V input-referred ripple. The AZ is duty cycled to minimize power and silicon area, with a parallel auxiliary path operating during AZ to keep the amplifier functioning properly. To improve the limited input signal range of conventional CFIA, an input common-mode (CM) voltage tracking circuit improves the input common-mode voltage range (CMVR) up to 42 V and CMRR to 132-dB, respectively. Further combined with source degeneration resistors, the input differential-mode voltage range (DMVR) is also increased to 800mV at 1% THD. The CFIA is implemented in a standard 0.18- $\mu $ m BCD process and consumes $294.5~\mu $ A. This translates into a competitive efficiency in terms of GBW/supply current of 134 kHz/ $\mu $ A.