determine the type of BJT

Thread Starter


Joined Mar 20, 2007
May I ask a question to you? Do you know a method to determine the type of the BJT (NPN or PNP)? If you can answer me as soon as possible, it ll be grate..


Joined May 16, 2005
Check it with an ohmmeter. (Use the search function for recent thread on how to do this.) Remember what you've learned about diodes.


Joined Mar 24, 2007
the arrow points to the N in NPN, but if your talking about using a real transistor, just ohm from collector to base & emitter to base, noting the polarity of the leads.


Joined Apr 16, 2007
In my EE lab we were given a bunch of BJT's and told to figure out what they were. They were a mix of different types (NPN or PNP) and differnt types... there were small ones, big ones, ones with only 2 terminals... ect.

Here is how we were told to do it.

We used a multimeter on the diode setting. Becuse of course you can model your NPN or PNP transistors using a set of opposing diodes. Cathode to Cathode or Anode to Anode.

So we would test the leads with the diode setting and see if there was a reading (voltage). We would ultimately try to narrow which pin was 'common' between the others and could call that our base.

(They just told us to apply our knowledge of diodes)

From there we would try to observe which way the flow would occur (by noticing which color lead from the meter was where on the transistor) and could determine if then the transistor was NPN or PNP.

They even threw in burned out transistors in the batch.

It very quickly became a group effort on our part.. and I hope ive given at least a start or a pointer into the correct direction.

Sorry for the vague description, because really it was a gaggle in our lab, and no one really had a clue what the hell was goin on.