A 40-<i>μ</i>V Offset 130-dB CMRR Analog Front End With Automatic Offset Calibration and Common Mode Cancellation for High-Precision Instrumentation Measurement

This article presents a fully-integrated high-precision analog-front-end (AFE), consisting of a three-opamp instrumentation amplifier (IA) followed by a 24-bit ΣΔ-ADC. An automatic-offset-calibration (AOC) as well as a common-mode-cancellation (CMC) techniques are proposed to improve the measurement accuracy. The prototype has been fabricated in an 180 nm BCD process, which achieves an input offset of 40 μV, an input impedance of 3.8 GΩ, and a CMRR of 130 dB. The peak SNR and SNDR is 106.2 dB and 95.4 dB , respectively, while obtaining a dynamic range of 110.5 dB. In a 3-leads Resistance-Temperature-Detector (RTD) temperature measurement experiment, the prototype achieves an accuracy of 0.03 °C within a temperature range of -40 °C to 160 °C, whereas in a full-bridge pressure measurement using strain gauges, the relative error ranges from -12.6 ppm to 39.0 ppm. The experimental results demonstrate the potential capability of the prototype to be widely adopted in high-precision instrumentation measurement.