Measurement of nanosecond-scaled reverse recovery time by a CPU-based instrument

Abstract

The dynamic characteristics imply the most important performance of semiconductor switching devices. Herein, a CPU-based instrument is designed for measuring the reverse recovery (RR) time (Trr) and RR charge (Qrr) of low power switching diodes. In the designed electrical system, the reverse voltage pulse is shaped by an emitter coupled logic (ECL) circuit constructed with microwave transistors to raise the pulse edges’ commutating-rate, which is applied to the device under test to yield the RR current (Irr) waveform. This waveform is converted into a voltage pulse with width equal to the RR time by voltage comparator consisted of the other ECL in the sampling circuit. This sampled pulse is sent to analog–digital converter and subsequently into an 89C2052-type CPU for calculating the values of Trr and Qrr, they are monitored by a liquid crystal displayer. The lowest metering range of about 3 ns of Trr is demonstrated, the displayed Trr value agrees with the one observed by oscilloscope, which verifies the design. Besides, the application of the ECL indicates a means of high-speed signal processing.