Optimal device for a low output impedance voltage source for Electrical Impedance Tomography (EIT) systems

The key component in bio-impedance measurement systems is an excitation source. Electrical Impedance Tomography (EIT) can be performed by injecting current and measuring the resulting voltages, or by applying voltages and measuring the current developed. Interesting characteristics of breast tissues mostly lie above 1MHz; therefore a wideband excitation source covering higher frequencies (i.e. above 1MHz) is required. A viable bandwidth envelope that can be used to design a constant EIT source having low output impedance is the main objective of this research. This paper proposes a voltage controlled voltage source (VCVS) tested by using different nonideal devices. The performance is compared with each other and decision is made which device can be used over a wide bandwidth (100Hz-20MHz) to design an excitation source. This paper also describes the performance of the designed EIT voltage source for different load conditions and load capacitances reporting signal-to-noise ratio, signal phase and output impedance of the source. Preliminary data obtained using Pspice is used to demonstrate the high-bandwidth performance of the source.