Junction Impedance Measurements of Diodes by a Simplified Lock-In Amplifier

A lock-in amplifier with most parts of its functional components substituted by integrated circuits is described here. This amplifier is far from expensive and is free from the trobles arising from temperature compensations and impedance matchings such as usually occur in conventional transistorized amplifiers. This instrument, operating at frequencies from 20 Hz to 100 kHz, has a noise rejection ratio of 40 dB and is suitable for junction capacitance and resistance measurement of diodes under reverse or forward bias.