Multi-channel biosignal recording systems that employ a shared-reference scheme and achieve high common-mode rejection ratio (i.e., CMRR > 80dB) have been reported in recent works. While it is well-understood that a shared-reference scheme causes impedance mismatch at the input terminals of bioamplifier, and thus limits the maximum achievable CMRR, a theoretical study that can provide quantitative assessment of this source of degradation is still lacking. This brief provides an equivalent electrical circuit model of the input interface consisting of an electrode array and bioamplifiers, followed by a complete analysis to formulate the CMRR degradation. Simulation results based on a previously designed and fabricated 32-channel neural recording front-end in a 180nm CMOS process are presented, exhibiting close agreement with the theory.

中文翻译：

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多通道生物信号记录系统中 CMRR 退化的分析

最近的工作报告了采用共享参考方案并实现高共模抑制比（即 CMRR > 80dB）的多通道生物信号记录系统。虽然众所周知，共享参考方案会​​导致生物放大器输入端的阻抗不匹配，从而限制了可实现的最大 CMRR，但仍缺乏可以对这种退化源进行定量评估的理论研究。本简介提供了由电极阵列和生物放大器组成的输入接口的等效电路模型，然后进行了完整的分析以制定 CMRR 退化。展示了基于先前设计和制造的 180 纳米 CMOS 工艺的 32 通道神经记录前端的仿真结果，与理论非常吻合。