Related Experiment Video
Updated: Aug 5, 2026

Characterization of Anisotropic Leaky Mode Modulators for Holovideo
Published on: March 19, 2016
A comparison of modified Howland circuits as current generators with current mirror type circuits
P Bertemes-Filho1, B H Brown, A J Wilson
1Department of Medical Physics and Clinical Engineering, Royal Hallamshire Hospital, University of Sheffield, UK. mpp98pb@sheffield.ac.uk
Abstract:
Multi-frequency electrical impedance tomography (EIT) systems require stable voltage controlled current generators that will work over a wide frequency range and with a large variation in load impedance. In this paper we compare the performance of two commonly used designs: the first is a modified Howland circuit whilst the second is based on a current mirror. The output current and the output impedance of both circuits were determined through PSPICE simulation and through measurement. Both circuits were stable over the frequency ranges 1 kHz to 1 MHz. The maximum variation of output current with frequency for the modified Howland circuit was 2.0% and for the circuit based on a current mirror 1.6%. The output impedance for both circuits was greater than 100 kohms for frequencies up to 100 kHz. However, neither circuit achieved this output impedance at 1 MHz. Comparing the results from the two circuits suggests that there is little to choose between them in terms of a practical implementation.
Related Concept Videos
DC Generator
Source Transformation
It is essential to note that when...
Source Transformation for AC Circuits
Norton Equivalent Circuits
Superposition Theorem for AC Circuits
The principle of superposition stipulates that the output of a linear circuit with several concurrent inputs is equivalent to the...
Equivalent Circuits for Practical Transformers
In a practical transformer, each winding exhibits resistance and leakage reactance. The winding...

