The capacitively coupled instrumentation amplifier (CCIA) is broadly used for neural signal acquisition. Although it is suitable for various biopotential recording applications, the CCIA is vulnerable to capacitor mismatches, which degrades the common-mode rejection ratio (CMRR). The neural signals with small amplitude can be easily contaminated by large-amplitude common-mode (CM) interferences due to the degraded CMRR. This brief presents a CMRR enhancement circuit for the CCIA, with which the capacitor mismatches can be compensated in a power-efficient manner. In the proposed CCIA, the gains of a pair of output stages are controlled separately to reject the output signals generated by the CM interferers in the presence of capacitor mismatches. Employing the proposed CMRR enhancement scheme, the implemented CCIA achieves a CMRR over 90 dB from 10 Hz to 1 kHz and 3.4- $\mu \text{V}_{\mathrm{ rms}}$ integrated input-referred noise (IRN) while only consuming $1.5~\mu \text{W}$ per channel.

中文翻译：

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采用 Gm 可控输出级用于电容耦合仪表放大器的 CMRR 增强电路

电容耦合仪表放大器 (CCIA) 广泛用于神经信号采集。尽管它适用于各种生物电位记录应用，但 CCIA 容易受到电容器不匹配的影响，这会降低共模抑制比 (CMRR)。由于 CMRR 降低，小幅度的神经信号很容易受到大幅度共模 (CM) 干扰的污染。本简介介绍了一种用于 CCIA 的 CMRR 增强电路，通过该电路可以以高能效的方式补偿电容器失配。在提议的 CCIA 中，一对输出级的增益是单独控制的，以在存在电容器失配的情况下抑制 CM 干扰产生的输出信号。采用提议的 CMRR 增强方案， $\mu \text{V}_{\mathrm{ rms}}$ 集成输入参考噪声 (IRN)，同时仅消耗 $1.5~\mu \text{W}$ 每个频道。