STIMULATOR CHARACTERISTICS
The input to the circuit, Vin, is a DC voltage which determines the excitation frequency. By placing a low frequency (approximately 40 Hz) square wave with proper offset, one may excite the body at two different frequencies. The stimulator generated both the in-phase and the out-of-phase components needed for the separation of the resistive and reactive components of tissue impedance. The current stimulating the subject is the in-phase sinusoidal. Patient isolation was provided by the use of an optically coupled amplifier on the stimulator side.