In this article, I will teach you how to test NPN and PNP Transistor which is the main reason you are here. After reading this article, you can determine if the transistor is an NPN or PNP Bipolar Junction Transistor (BJT).
First of all, any transistor you wish to test if it is an NPN Bipolar Junction Transistor (BJT) or PNP BJT, I would recommend that it should not be connected in the circuit. The reason is that, the effects of other electronic components in the circuit may affect the acurate result. So, we had made sure that it is removed from the circuit.
Alright! Let me move you straight to the steps how to test NPN and PNP Transistor. Meanwhile, to understanding more about NPN and PNP Transistors, read this article. This is because I will not explain it in this very article you are reading.
Steps to test NPN and PNP BJTs
We are going to use a digital multimeter which is more convinient for this task. But however, if you don’t have one, don’t worry! You can use an analog multimeter which also works fine.
Step1
Make sure the Black Probe of the multimeter is connected to “COM” port and Red Probe to “VΩmA” port of the multimeter.
Step2
Turn your multimeter to Continuity or Diode Tester Range or Resistor Testing range at 2000Ω (2KΩ) range.
Step3
Place the Red Probe at the first pin of the transistor and the Black Probe at the second (middle) pin. Observe the reading or the deflection on the multimeter. By reversing the Probes, test again and observe the reading or deflection. If it reads or deflects at both forward and reverse testing, the BJT is bad. However, if it reads or deflect at only one direction or did not read or deflect at all, move to the next step. Do reverse testing in all the below steps (Step4, 5, 6, 7, and 8) as well and if it reads at both reverse and non reverse testing, it means the BJT is bad.
Step4
With the Red Probe on the first pin again, move the Black Probe to the third pin, observe if there is reading or not.
Step5
Take the Red Probe to the second (middle) pin and Black to the third pin. Observe the reading or deflection
Step6
With the Red Probe on the second (middle) pin, move the Black Probe to the first pin. Observe the reading or deflection
Step7
Place the Red Probe at the third pin where the Black on the first pin. Observe the reading or deflection
Step8
Finally, with the Red on the third pin, move the Black Probe from the first pin to the second (middle) pin, observe the reading or the deflection. Don’t forget to also reverse the probes and test again.
Use the table of how to test NPN and PNP Transistor below to determine if it’s an NPN or PNP Bipolar Junction Transistor. The digits 1, 2, and 3 signifies the transistor’s pins and R or B means Red probes and Black probes respectively under each pin.
Note that Transistors have different pin configurations but they all have THREE PINS. Don’t forget to share!
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