[Study on double feedback current source for biologic impedance measurement].

A double feedback current source for biologic impedance measurement is designed in order to solve the problem on the poor constant-current characteristic under higher frequency and meet the request for the ability to eliminate the direct current signal. The voltage controlled current source based on the second generation current conveyor theory is presented, which has good output impedance and anti-direct current characteristics by using the direct current feedback unit and input buffer. The closed loop control of current amplitude is implemented by means of the direct digital synthesizer and multiplication demodulation technique, which improves the constant-current characteristic of the current source.