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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).
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...
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...
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