Chapter

13th International Conference on Electrical Bioimpedance and the 8th Conference on Electrical Impedance Tomography

Volume 17 of the series IFMBE Proceedings pp 213-216

A Comprehensive Study on Current Source Circuits

  • W WangAffiliated withBiomedical Engineering Group, School of Engineering and Technology, De Montfort University
  • , M. BrienAffiliated with2Control & Instrumentation Research Group, Dept of Engineering,, University of Leicester
  • , D-W GuAffiliated with2Control & Instrumentation Research Group, Dept of Engineering,, University of Leicester
  • , J Yang Affiliated withBiomedical Engineering Group, School of Engineering and Technology, De Montfort University

* Final gross prices may vary according to local VAT.

Get Access

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.