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How to identify a transistor if it is a npn or pnp type with help of a multimeter

Tags: help of a multimeter, transistor, pnp type
Asked by arvind kumar, 11 Apr '07 10:40 am
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Answers (3)


You will need the following:
1 multimeter that has a diode test function [Fig.2].

1 9V battery
1 1K resistor
Some hookup wire.
Now for the first part - determining whether the transistor is NPN or PNP. Grab your multimeter, and set it to diode test. Place the transistor on a table with its markings on the top. Now test all the different combinations of legs that the transistor has. Consider the legs from left to right as leg 1, leg 2, leg 3.

If you label the three legs leg 1, leg 2 and leg 3, then you test the continuity of:
1 to 2
2 to 1
1 to 3
3 to 1
2 to 3
3 to 2

If the transistor is working, then you will have gotten a value of about 0.5 - 0.7 volts for two of the six tests. The rest of the tests should have said that there is infinite resistance between the legs tested. If you get more than two positive results, or you get less than 2 positive results, then the transistor is fried.
What's more, the two tests that return a positive result will h ...more
Answered by rathindranath datta, 11 Apr '07 11:12 am

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We can identify a transistor for NPN or PNP type with a multimeter itself.
1) Multimeter
2) Transistors to be identified

It would be very easy if the terminals are already known. (Emitter, base and collector) . If yes,
Put the multimeter in the Resistance measurment mode. Connect the negative probe to the base and positive probe to the Emitter first and then to the collector next. If both are showing a forward bias then the transistor is PNP.
If the Base is with Positive probe and the negative probe to emitter and collector gives a forward bias then it is NPN.

If the terminals are not known, then we need to identify the base first as above that with one lead in common it should have forward bias to the other two leads. The collector can be identified by the reverse resistance. The reverse resistance between collector and and base will be higher than the reverse resistance between emitter and base. There should not be any resistance shown between collector an ...more
Answered by Murali K, 16 Apr '07 08:25 pm

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on a multimeter ,there is one (say) section viz. npn & pnp. you can fixed the transistor in one of them & if u get the some value in ohms then the transistor is of that type otherwise other type.
Answered by Shweta Patil, 22 Apr '07 11:35 pm

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