<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Bioimpedance measurements use current or voltage sources to inject an excitation signal into the body. These sources require a high bandwidth, typically from 1 kHz to 1 MHz. Besides a low common mode, current limitation is necessary for patient safety. In this paper, we compare a symmetric enhanced Howland current source (EHCS) and a symmetric voltage source (VS) based on a non-inverting amplifier between 1 kHz and 1 MHz. A common mode reduction circuit has been implemented in both sources. The bandwidth of each source was optimized in simulations and achieved a stable output impedance over the whole frequency range. In laboratory measurements, the output impedance of the EHCS had its -3 dB point at 400 kHz. In contrast, the VS reached the +3 dB point at 600 kHz. On average over the observed frequency range, the active common mode compensation achieved a common mode rejection of -57.7 dB and -71.8 dB for the EHCS and VS, respectively. Our modifications to classical EHCS and VS circuits achieved a low common mode signal between 1 kHz and 1 MHz without the addition of complex circuitry, like general impedance converters. As a conclusion we found VSs to be superior to EHCSs for bioimpedance spectroscopy due to the higher bandwidth performance. However, this only applies if the injected current of the VS can be measured.</p></abstract>

Bioimpedance measurements use current or voltage sources to inject an excitation signal into the body. These sources require a high bandwidth, typically from 1 kHz to 1 MHz. Besides a low common mode, current limitation is necessary for patient safety. In this paper, we compare a symmetric enhanced Howland current source (EHCS) and a symmetric voltage source (VS) based on a non-inverting amplifier between 1 kHz and 1 MHz. A common mode reduction circuit has been implemented in both sources. The bandwidth of each source was optimized in simulations and achieved a stable output impedance over the whole frequency range. In laboratory measurements, the output impedance of the EHCS had its -3 dB point at 400 kHz. In contrast, the VS reached the +3 dB point at 600 kHz. On average over the observed frequency range, the active common mode compensation achieved a common mode rejection of -57.7 dB and -71.8 dB for the EHCS and VS, respectively. Our modifications to classical EHCS and VS circuits achieved a low common mode signal between 1 kHz and 1 MHz without the addition of complex circuitry, like general impedance converters. As a conclusion we found VSs to be superior to EHCSs for bioimpedance spectroscopy due to the higher bandwidth performance. However, this only applies if the injected current of the VS can be measured.

Bandwidth and Common Mode Optimization for Current and Voltage Sources in Bioimpedance Spectroscopy

Journal of Electrical Bioimpedance

This work is licensed under the Creative Commons Attribution 4.0 International License.

Bioimpedance measurements use current or voltage sources to inject an excitation signal into the body. These sources require a high bandwidth, typically from 1...

Bandwidth and Common Mode Optimization for Current and Voltage Sources in Bioimpedance Spectroscopy

Published Online: Dec 27, 2021

Page range: 135 - 146

Received: Jul 05, 2021

DOI: https://doi.org/10.2478/joeb-2021-0016

Keywords
bioimpedance spectroscopy, enhanced Howland current source, voltage source, common mode reduction, output impedance, harmonic distortion

© 2021 Tobias Menden, Jascha Matuszczyk, Steffen Leonhardt and Marian Walter, published by Sciendo

This work is licensed under the Creative Commons Attribution 4.0 International License.

Bandwidth and Common Mode Optimization for Current and Voltage Sources in Bioimpedance Spectroscopy

Published Online: Dec 27, 2021

Page range: 135 - 146

Received: Jul 05, 2021

DOI: https://doi.org/10.2478/joeb-2021-0016

Keywordsbioimpedance spectroscopy, enhanced Howland current source, voltage source, common mode reduction, output impedance, harmonic distortion

© 2021 Tobias Menden, Jascha Matuszczyk, Steffen Leonhardt and Marian Walter, published by Sciendo

This work is licensed under the Creative Commons Attribution 4.0 International License.

Keywords
bioimpedance spectroscopy, enhanced Howland current source, voltage source, common mode reduction, output impedance, harmonic distortion