Impedance measuring circuit for semiconductor components - has summing circuit forming dipole equivalent to voltage generator in combination with pulse generator and oscillator

摘要

The appts. produces on image of the relaxation curve of a component under the influence of an electric perturbation, the image reproducing faithfully rapid impedance variations with a response time less than 100 nS. The appts. has an oscillator (1) emitting a carrier of known frequency and a pulse generator (2) emitting a polarisation signal with predetermined rise edge. A summation circuit (3) delivers a signal representing the sum of the oscillator and pulse generator signals to the impedance to be measured (C). The oscillator, pulse generator and summation circuit together form a dipole equivalent to a voltage generator having negligible output impedance w.r.t. the impedance to be measured. The appts. also has an amplifier (5) tuned to the carrier frequency and connected to the output of the impedance to be measured, an adjustable phase convertor (7) which receives the carrier signal and delivers a signal whose phase is adjustable w.r.t. the signal from the amplifier a demodulator (6) which receives signals from the amplifier and phase convertor and delivers a signal proportional to the product of these two signals to a low-pass filter (8) which eliminates the carrier frequency component.