The JT 777 is used to test diodes according to JEDEC Standard No. 282B.01. This describes the stress on diodes caused by alternating forward and reverse operation in the limit area of the component.

The JT 777 combines generators, measuring devices, switching and control in one device.

To determine the forward voltage, a sinusoidal or rectangular load current pulse of up to 400 A is passed through the test object.

With a sinusoidal current, the voltage is measured at the current maximum of the half-wave, with a square-wave pulse approx. 1 ms before the end of the pulse.
The test current is taken from a switching power supply in constant current mode. The internal current measurement is carried out via shunts.

To determine blocking currents and blocking voltages, the test object is operated with a sinusoidal or square-wave high-voltage pulse of up to 2,000 V.