I have a circuit where a 5.055V 2.17A (MAX) DC circuit is supposed to be switched using a 3.404V 0.99A(MAX) DC source.
Theoretically, 3.404V 0.99A between base and emitter should allow quite a large current to pass from collector to emitter, but when I am using BC548 B type (Min theoretical gain 200X) as my transistor, the Collector-emitter current that I am actually getting is only about 1.34A.
Of course, BC548 is not designed to handle that high level of current. So I replaced it with TIP31C O Type (Min gain 20X), but something strange hapened with the TIP31C. That transistor is passing at least 1.63A between collector and emitter even when there is nothing connected to base and therefore no potential difference is going on between base and emitter.
Admittedly, I do not know how to read all the parameters on a transistor datasheet, but even the BC548 did not break down at that voltage, and there is no OFF characteristic mentioned on the TIP31C datasheet at all.
Not only that, even after applying the 3.404V 0.99A potential difference between base and emitter, the collector-emitter current is only going up to 1.72A.
Is there any theoretical explanation behind this strange behaviour?