Can you help me test a transistor

[r2pee3]

I have a mpsw45a transistor npn . I need to test it with multimeter to see if its good. When I use a multimeter to test it, positive on base and neg on collector I get a value however when I move the neg to emitter there is no value. I am a newb so maybe I am not doing this correctly. Thanks

 

[BobK]

I assume you mean using the diode test function of your multimeter, correct?

If so, you should get something like 0.6V on both of those connections. If you get nothing with the base positive and emitter negative, the transistor is bad.

Oh, and welcome to E.P.

Bob

 

[r2pee3]

Hello Bob,
I bought 5 brand new transistor and all of it are testing the same. I have it set on diode test fnction.
Thanks

 

[BobK]

Are you sure you are identifying the pins correctly?

What kind of transistor?

Bob

 

[r2pee3]

This is a mpsw45a npn darlington ss 1a 50v 1

 

[Audioguru]

The datasheet from Motorola shows the schematic of its insides and its pins.
It has one silicon junction between its base and its collector with a forward voltage of about 0.65V. It has two silicon junctions in series between its base and emitter with a total forward voltage of about 1.3V that your multimeter diode test might not show.

 

[Colin Mitchell]

You need to put the transistor in a circuit with a 12v car globe (one of the globes for the inside light. )
Put 4k7 on the base and the 12v rail. The lamp will illuminate.
If it was a normal transistor, the lamp would not glow.
This is a Darlington.

 

[r2pee3]

The datasheet from Motorola shows the schematic of its insides and its pins.
It has one silicon junction between its base and its collector with a forward voltage of about 0.65V. It has two silicon junctions in series between its base and emitter with a total forward voltage of about 1.3V that your multimeter diode test might not show.

That explains why. Thank you very much