<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Multifrequency Electrical Bioimpedance (MEB) has been widely used as a non-invasive technique for characterizing tissues. Most MEB systems use wideband current sources for injecting current and instrumentation amplifiers for measuring the resultant potential difference. To be viable current sources should have intrinsically high output impedance for a very wide frequency range. Most contemporary current sources in MEB systems are based on the Howland circuit. The objective of this work is to compare the Mirrored Modified Howland Current Source (MMHCS) with three Operational Transconductance Amplifier (OTA) based voltage controlled current sources (i.e., class-A, class-AB and current conveyor). The results show that both current conveyor and class-AB OTA-based current sources have a wider output current frequency response and an output impedance of 226% larger than the MMHCS circuit at 1 MHz. The presented class-AB OTA circuit has a power consumption of 4.6 mW whereas current conveyor consumed 1.6 mW. However, the MMHCS circuit had a maximum total harmonic distortion of 0.5% over the input voltage from -0.5 to +0.5 V. The OTA-based current sources are going to be integrated in a semiconductor process. The results might be useful for cell impedance measurements and for very low power bioimpedance applications.</p></abstract>

Multifrequency Electrical Bioimpedance (MEB) has been widely used as a non-invasive technique for characterizing tissues. Most MEB systems use wideband current sources for injecting current and instrumentation amplifiers for measuring the resultant potential difference. To be viable current sources should have intrinsically high output impedance for a very wide frequency range. Most contemporary current sources in MEB systems are based on the Howland circuit. The objective of this work is to compare the Mirrored Modified Howland Current Source (MMHCS) with three Operational Transconductance Amplifier (OTA) based voltage controlled current sources (i.e., class-A, class-AB and current conveyor). The results show that both current conveyor and class-AB OTA-based current sources have a wider output current frequency response and an output impedance of 226% larger than the MMHCS circuit at 1 MHz. The presented class-AB OTA circuit has a power consumption of 4.6 mW whereas current conveyor consumed 1.6 mW. However, the MMHCS circuit had a maximum total harmonic distortion of 0.5% over the input voltage from -0.5 to +0.5 V. The OTA-based current sources are going to be integrated in a semiconductor process. The results might be useful for cell impedance measurements and for very low power bioimpedance applications.

Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits

Journal of Electrical Bioimpedance

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Multifrequency Electrical Bioimpedance (MEB) has been widely used as a non-invasive technique for characterizing tissues. Most MEB systems use wideband current...

Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits

Article Category: Articles

Published Online: Oct 23, 2012

Page range: 66 - 73

Received: Jun 29, 2012

DOI: https://doi.org/10.5617/jeb.380

Keywords
Howland circuit, OTA, current conveyor, bioimpedance

© 2012 Pedro Bertemes-Filho, Volney C. Vincence, Marcio M. Santos, Ilson X. Zanatta, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits

Article Category: Articles

Published Online: Oct 23, 2012

Page range: 66 - 73

Received: Jun 29, 2012

DOI: https://doi.org/10.5617/jeb.380

KeywordsHowland circuit, OTA, current conveyor, bioimpedance

© 2012 Pedro Bertemes-Filho, Volney C. Vincence, Marcio M. Santos, Ilson X. Zanatta, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig.1

Fig.2

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Fig.4

Fig.5

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Fig.7

Fig.8

Keywords
Howland circuit, OTA, current conveyor, bioimpedance