A Comprehensive Study on Current Source Circuits

  • W Wang
  • M. Brien
  • D-W Gu
  • J Yang
Part of the IFMBE Proceedings book series (IFMBE, volume 17)

Abstract

A current source is one of the key components in an EIT system, particularly in EIT based breast imaging which is called electrical impedance mammography (EIM). It is also a critical source of systematic errors due to limited output impedance and associated frequency bandwidth. One method for increasing the output impedance is a Generalised Impedance Converter (GIC). This paper investigates two Howland-based, voltage-to-current conversion (V/I) circuits; one is a simple, optimized current source developed by the Leicester Group while the other includes a GIC. This investigation evaluates both circuits using PSpice, measuring output impedances at 1KΩ loading along with -3dB and -1dB bandwidths; these are of clinical interest, as EIT needs to cover a wide range of frequencies. It was expected that the GIC would increase the output impedance with required frequency bandwidth. The results show that, the GIC has improved the output impedance, reaching 120MOhm. However, the high output impedance was only for a limited bandwidth.

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References

  1. 1.
    P Bertemes-Filho et al. (2000) A comparison of modified Howland circuits as current generators with current mirror type circuits. Physiol Meas 21:1–6.CrossRefGoogle Scholar
  2. 2.
    Ross A S et al. (2003) Current source design for electrical impedance tomography. Physiol Meas 24:509–5.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2007

Authors and Affiliations

  • W Wang
    • 1
  • M. Brien
    • 2
  • D-W Gu
    • 2
  • J Yang
    • 1
  1. 1.Biomedical Engineering Group, School of Engineering and TechnologyDe Montfort UniversityLeicester,UK
  2. 2.2Control & Instrumentation Research Group, Dept of Engineering,University of Leicester LeicesterUK

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