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Last Updated on: Tuesday, November 29, 2011 08:14 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 Drawing Below to view PDF version of Schematic

Circuit npn-pnp transistor tester circuit

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