PNP vs NPN: How to spot a Transistor is NPN or PNP

All transistors are divided into two types. They are either NPN or PNP. In this post, you’ll learn how to spot/identify an NPN or PNP Transistor.

You need a Digital Multimeter which has a diode test for this experiment. Follow these steps:

  1. Set the multimeter to diode setting.
  2. Connect red probe to V setting.
  3. Connect black probe to the Common terminal.
  4. Identify the base, collector, emitter of the transistor. Usually, the central terminal is the base.
pnp-vs-npn-transistor-how-to-identify

How to Identify NPN Transistor

  1. Connect the red probe to the base and black to the collector. Some value will appear.
  2. Connect red to base and black to the emitter. Some value will appear.
  3. Connect red to the emitter and black to the base. No value appears.
If the multimeter works other than above, it is PNP.

How to identify PNP Transistor

  1. Connect red to the base and black to the collector. No value appears.
  2. Connect red to base and black to the emitter. No value appears.
  3. Connect red to the emitter and black to the base. It will indicate some value.

Conclusion

One can easily understand from above knowledge that we are actually detecting the PN junction which is either forward biased or negative biased. You can simply use your knowledge of diode to perform the test any way. Let’s watch a practical illustration of how this is actually done.

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