COMMON-MODE FEEDBACK AMPLIFIER FOR BIOIMPEDANCE MEASUREMENTS

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.

[1]  D S Holder,et al.  Current approaches to analogue instrumentation design in electrical impedance tomography , 1996, Physiological measurement.

[2]  J P Morucci,et al.  Bioelectrical impedance techniques in medicine. Part III: Impedance imaging. Second section: reconstruction algorithms. , 1996, Critical reviews in biomedical engineering.

[3]  A Hartov,et al.  Dartmouth's next generation EIS system: preliminary hardware considerations. , 2001, Physiological measurement.

[4]  H Scharfetter,et al.  A model of artefacts produced by stray capacitance during whole body or segmental bioimpedance spectroscopy. , 1998, Physiological measurement.

[5]  J Rosell,et al.  Common-mode feedback in electrical impedance tomography. , 1992, Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics.

[6]  J. Rosell,et al.  Multi-frequency static imaging in electrical impedance tomography: Part 1 instrumentation requirements , 1995, Medical and Biological Engineering and Computing.