How to find transistors Emitter, Base, and Collector with Multimeter?

Abhimanyu's picture
Joined: Sep 14, 2018
Replies: 0
How to find transistors Emitter, Base, and Collector with Multimeter?
September 14, 2018 - 12:18pm

I was wondering that if i dont have datasheet of a particular transistor. Which is sometimes not even available on internet..

Then how we can check the pinout of transistors.

Can we use multimeter for the same or there is any other way to find..


B.Aswinth Raj's picture
Joined: Aug 16, 2016
Replies: 740
Transistor pinout using Multimeter
September 15, 2018 - 11:04am

Hi Abhimanyu, welcome to circuit digest forums ...


The best and quickest way to find the pinout of any component is to do a quick google search or by checking its dasheet.

But lets assume you are left only with a multimeter and a transistor and have no signal for internet this technique can help you


Finding pinout for metal casing transistor:

If you transistor is metal cased, then you work is reduce by more than half. Simply put your multi-meter in continuity mode and check which pin is in connecting with the metal casing. This pin will be you collector. Now put the meter in diode mode and check the other two pins, if the positive lead is placed on the base and the negative on emitter then you meter will read a voltage drop of 0.5 to 0.7 for a NPN transistor. Its just the inverse for PNP.


Finding pinout for normal transistors:

Alas! if you transistor is not metal cased you have to go through a tiring process. The following is for NPN transistor. Put you meter in diode mode and try the pin combinations for pins 1+2, 1+3, and 2+3 since the transistor is a NPN transistor at one pin for both forward and reverse ou will get a voltage drop of 0.5 to 0.7 V. Thi spin your base pin. Since the combination is NPN transistor that is it has a diode in either direction.

Now we have to find the emitter and collector pin. For this place your positive lead on base pin and check for voltage dorp on diode mode for the other pins. The pin with higher voltage drop will be your emitter and the other will be your collector. do take this with a pinch of salt as it not a very reliable method it depends on how good your multimeter is.

Use these methods only when you do not have other options