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 to load and instrumentation amplifiers for measuring the resultant potential. Current sources should present intrinsically high output impedance in a very wide frequency range. The objective of this work is to investigate the performance of the Mirrored Modified Howland Current Source (MMHCS) by comparing the analytical solution with the SPICE simulation. It was implemented four MMHCS circuits by using four different operational amplifiers each one. The output current was set to 1 mAp (peak) in the frequency from 1 Hz to 100 MHz. Both techniques presented similar results at lower frequencies. It can be concluded that the output impedance of the circuit is highly dependent of the open-loop gain of the operation amplifier. The analytical solution showed that it is possible to project a current source by using only theirs output current and impedance equations.
Export citation and abstract BibTeX RIS