OTA based Howland model for bio-electrical impedance spectroscopy

Bio-electrical impedance measures the impedance of living tissues to the flow of a harmless alternating electrical current. For this purpose we need a current source, the most important circuit block of a bio-electrical impedance measurement system. Such a current source is required to have large output impedance and should be able to supply a constant output current in a wide frequency range. In this paper, we have introduced the design of an improved Howland current source using OTA (Operational Transconductance Amplifier) and compared its performance with the conventional Improved Howland model over a wide frequency range of 10 kHz to 1MHz. The simulation results show that our current source is able to provide a stable output current below 1mA for loads varying from 1kΩ to 10kΩ.