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# How can i test a transistor??

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#### wini-1

##### Junior Member level 2
Hi,

I have two transistor NPN & J-FET , How can i test each one to know if they works or not??

thanx.

Most multimeters will test a npn for you.

But the easiest way would be just design a simple emmiter follower or the like, breadboard it and see if it behaves as expected. You'll need a sig-gen and a scope for this, (you could do it with a DC input and volt meter too I suppose). These circuits and their expected behaviour can be found in seconds with a google search.

With a Digital multimeter checking of NPN transistor is easy and as follows:
Set the meter to a diode check. And put the +ive lead on the base of the transistor and -ive on the emitter, it should show for a good transistor a drop between 0.4V to 0.8V and put the -ive lead on collector, same should show. (only difference with minor voltage say B-E=0.560V then B-C=0.540V). If you reverse the leads then no drop should be displayed for a good transistor. And also check C-E leads, it is also not show any drop if transistor is good (provided there is no diode internally connected between C and E).

Regards

hi there,

the most primitive way of testing a transistor is to test each junctions' resistance...

note that a working diode has a forward resistance and it has a reverse resistance equivalent to infinity...

here's what to do, measure the forward and reverse resistance of each of the junction... a non-working transistor will have at least one of the junctions' resistance equivalent to zero value... or both forward and reverse resistance of a junction equal to infinity...

note: a basic VOM will do...

hope it helps...

hi there,

the most primitive way of testing a transistor is to test each junctions' resistance...

note that a working diode has a forward resistance and it has a reverse resistance equivalent to infinity...

here's what to do, measure the forward and reverse resistance of each of the junction... a non-working transistor will have at least one of the junctions' resistance equivalent to zero value... or both forward and reverse resistance of a junction equal to infinity...

note: a basic VOM will do...

hope it helps...

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