for example...method 1by triggering base, we switch on a larger voltage by sinking? eg + side of the led would go to the 5v+ rail... useful as, to power devices with a higher voltage rating...but..method 2current gain? 1ma 100ma to power an led? which is better? and how do you decide which method is the best ?
There are two types of transistors, which have slight differences in how they are used in a circuit. A bipolar transistor has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain.
I'll leave it But Bipolar transistor are current controlled
i was overly thinking it ....what my question should have asked....when to sink/source ? how to know which to use? (in relation to the fact the main power supply would be 5v)use the transistor sourceoruse the transistor as a sinkboth 5v suppliesor does it really not matter? cheers