Comparison of a new integrated current source with the modified Howland circuit for EIT applications

Hong, Hongwei and Rahal, Mohamad and Demosthenous, Andreas and Bayford, Richard (2009) Comparison of a new integrated current source with the modified Howland circuit for EIT applications. Physiological Measurement, 30 (10). pp. 999-1007. ISSN 0967-3334

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Multi-frequency electrical impedance tomography (MF-EIT) systems require current sources that are accurate over a wide frequency range (1 MHz) and with large load impedance variations. The most commonly employed current source design in EIT systems is the modified Howland circuit (MHC). The MHC requires tight matching of resistors to achieve high output impedance and may suffer from instability over a wide frequency range in an integrated solution. In this paper, we introduce a new integrated current source design in CMOS technology and compare its performance with the MHC. The new integrated design has advantages over the MHC in terms of power consumption and area. The output current and the output impedance of both circuits were determined through simulations and measurements over the frequency range of 10 kHz to 1 MHz. For frequencies up to 1 MHz, the measured maximum variation of the output current for the integrated current source is 0.8% whereas for the MHC the corresponding value is 1.5%. Although the integrated current source has an output impedance greater than 1 MΩ up to 1 MHz in simulations, in practice, the impedance is greater than 160 kΩ up to 1 MHz due to the presence of stray capacitance.

Item Type:Article
Research Areas:School of Science and Technology > Natural Sciences
Citations on ISI Web of Science:2
ID Code:3598
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Deposited On:11 Jan 2010 05:17
Last Modified:29 Oct 2013 07:44

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