PNP or NPN???

[green]

Hi there,

I got a transistor, but I do not know whether is is a NPN or PNP. Anyone know how to determine the transistor type with multimeter ? Thanks.

green

 

[Nigel Goodwin]

Hi there,

I got a transistor, but I do not know whether is is a NPN or PNP. Anyone know how to determine the transistor type with multimeter ? Thanks.

green

It depends on your particular multimeter, different types output different polarities - it's best to test a known transistor, to see which way round it works. Essentially a transistor tests as two diodes, with the base common, so it should read from both base to emitter, and base to collector, one way round - and not at all the other.

 

[thomas_tiger]

Some multimeters have a transistor check socket, it may be useful to you.
I agree with what Nigel wrote above or you can read this information on transistor http://www.geocities.com/bagtool/trans_check.html

cheers...

thomas.

 

[Exo]

what markings does it have ?

 

[Jay.slovak]

You can test that transistor as it's like two diodes in one package....

 

[fsahmed]

You can test that transistor as it's like two diodes in one package....

In addition, remember that the diode from collector to base has less junction voltages than the emitter to base diode, should u use diode tester that gives junction voltages (knee voltages) as well. This is because emitter is heavily biased as compared to the collector.

 

[Nigel Goodwin]

You can test that transistor as it's like two diodes in one package....

In addition, remember that the diode from collector to base has less junction voltages than the emitter to base diode, should u use diode tester that gives junction voltages (knee voltages) as well. This is because emitter is heavily biased as compared to the collector.

I didn't know that? - I'll have to give it a try!.

 

[Jay.slovak]

You can test that transistor as it's like two diodes in one package....

In addition, remember that the diode from collector to base has less junction voltages than the emitter to base diode, should u use diode tester that gives junction voltages (knee voltages) as well. This is because emitter is heavily biased as compared to the collector.

I didn't know that? - I'll have to give it a try!.

Yes, it's a pretty comon practice when one doesn't know the transistor type. Interesting to see that you didn't know this :wink: (considering your many years of experience, no offense).

 

[eblc1388]

Just measured three transistors, using the "diode" range on a DVM.

2SB621: PNP small signal, difference of 5mV
2N5551: NPN small signal, difference of 8mV
NPN TO3 size, unknown part number: difference 3mV

I think I will stick to my "beta" measurment method which served me good for many years and which gives a very big difference than the above.

 

[Nigel Goodwin]

I've just tried a BC107 (NPN), it reads 15mV higher BE than BC, I agree with 'eblc1388', I'll stick to beta tests if I ever need to do this :lol:

 

[fsahmed]

Just measured three transistors, using the "diode" range on a DVM.

2SB621: PNP small signal, difference of 5mV
2N5551: NPN small signal, difference of 8mV
NPN TO3 size, unknown part number: difference 3mV

I think I will stick to my "beta" measurment method which served me good for many years and which gives a very big difference than the above.

But the point is that it works!!!!

 

[eblc1388]

But the point is that it works!!!!

Calm down. Never said it doesn't otherwise.

But it doesn't work on my multimeter(with a pointer) that I use 99% of the time for troubleshooting and testing LEDs.

 

[Nigel Goodwin]

But it doesn't work on my multimeter(with a pointer) that I use 99% of the time for troubleshooting and testing LEDs.

Presumably it's the 'youngsters' brought up on digital meters that know about this?, us 'oldies' brought up on analogue meters don't know about it, because it wasn't possible to measure!.

 

[i_build_stuff]

Speaking of modern equipment, some transistor checkers will give the type (npn or pnp), pinout and dc gain all in one shot.

 

[Nigel Goodwin]

Speaking of modern equipment, some transistor checkers will give the type (npn or pnp), pinout and dc gain all in one shot.

Yes, there's a small company not too far from me that manufactures them (amongst other test equipment), and they are built around PIC's :lol:
https://www.peakelec.co.uk

Just had a quick measure, it's about 22 miles away, as the crow flys!.

 

[atferrari]

Sometimes also...

When you don't know yet which one is emitter and which one colector, you put your multimeter between them to measure resistance.

Then with your finger more or less humid (wet?), you alternatively shortcircuit each one with the base. When you see a change in the measurement, you have identified the collector.

Obviously, polarity between emitter and collector should allow this.

Long time I don't do this but used it many times in the past.

If I recall properly, didn't work with power transistors...