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提出了一种采用共模复制技术的仪表放大器，实现了130dB CMRR。该技术同时提升固有CMRR和输入共模阻抗，有效抑制源阻抗不平衡导致的CMRR退化，适用于高阻抗传感器前端。
Interfacing with high-impedance sensors, such as dry-contacted electrodes and accelerometers requires high CMRR with sufficient input impedance concurrently. From the system point of view, the total CMRR (TCMRR) is determined by the intrinsic CMRR (ICMRR) of the front-end amplifier as well as the imbalance of source impedance; the latter has to be accommodated by large input commonmode (CM) impedance (ZIN,CM). Widely adopted CMRR enhancement techniques, i.e., chopping, common-mode feedback (CMFB), common-mode feedforward, improve ICMRR only [1-3]. Positive feedback improves the input differential-mode (DM) impedance (ZIN,DM) effectively [4]. However, it is the input CM impedance that contributes to the TCMRR, which has not been commonly noted. Singleended amplifiers, e.g., active electrodes (AE) [3,5], and traditional 3-opamp instrumentation amplifiers do not suffer from the confusion, where the ZIN,CM and
Sanfeng Zhang, Chen Gao, Xiong Zhou, Qiang Li
University of Electronic Science and Technology of China, Chengdu, China