Common-Mode Feedback Amplifier for Bioimpedance Measurements

I.-D. Hwang (Korea)


Bioimpedance, common-mode feedback, common-modevoltage, CMMR


A new stable wideband common-mode feedback for accurate bioimpedance measurements has been introduced. This employs a feedback amplifier that amplifies the common-mode voltage phase-sensitively. Voltage gain of the proposed amplifier has a sharp peak at the frequency of the input signal (the common-mode voltage). Crossover frequency of the feedback amplifier is near the frequency of the input signal. Thus, the loop gain of the feedback loop incorporating the amplifier can be increased without introducing instability at high frequency. The feedback loop including the proposed feedback amplifier was analyzed with a linear model. The result was coincided with the one by a circuit simulation. A stable wideband operation and reduction of the CMV were verified experimentally using an implemented circuit.

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