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Last Updated on: Tuesday, June 01, 2021 03:06 PM

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More  Tester Circuits

NPN-PNP Transistor Tester
designed by David Johnson, P.E.

I designed this hobby electronic circuit about 30 years ago and still use it from time to time. It is powered from a 3v battery. It makes a tone when the transistor tests good. It can be used to determine device type (NPN or PNP) and the base, collector or emitter transistor pins. It can also test most transistors while still connected to a circuit.

Click on Circuit Below to view PDF of Schematic


npn-pnp transistor tester circuit



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