PN Junction tester

This transistor tester tests bipolar junction transistors junctions. It tests the junctions for open and short circuits. It uses 4 resistors, 4 LEDs and 1 SPDT switch. A good transistor will only have 2 out of 4 LEDs lit, on one side of the switch and 4 on the other. You can also test standard diodes (rectifiers and switching diodes). A diode will have 3 out of 4 LEDs lit on one side and 4 on the other.

Here’s a table of all possible readings and their meanings

2 LED lit

Both emitter/collectors are short circuited

3 LEDs lit

Only one emitter/collector

4 LEDs lit

Open circuit

1 LED lit

Circuit design error

Published by Justin Roeder

I am an electronics engineer and computer programmer that has autism. I learned by myself

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