Using a FET to switch a higher current.

There are, as you noted, 3 terminals. How you connect them depends on the circuit. The gate is usually the control terminal. Drain and source connections depend on other things in this case, so it's not possible to say.

Beyond that, I don't think I can help without knowing the part and more details of the application.

Switching high or low side? Run current? Run voltage? (You'll have to protect against reverse emf too)

For a search, google is your friend:

(FET basics)

In this particular case, you are probably using a MOSFET, so :

Search under 'MOSFET basics' and you'll bring up thousands of hits.

Do that, then come back and ask some more. We tend to be more forthcoming for people who have done at least some legwork trying to figure things out.

Cheers

PeteS

Why do you call it "simple" when you don't have the least idea what it is, what it does, or how to go about using it? You're an arrogant pea-brain from hell.

sci.electronics.basics

To make it as simple as possible a MOSFET is like a transistor except that it is controlled by a voltage, and it isnt variable like a transistor is, it is only ON or OFF. This site gives some more info:

Huh? Actually, the "T" in MOSFET stands for "Transistor". A MOSFET is a transistor. I'm not sure where you got the idea that it's not. Technically speaking, MOSFET's have more regions than the two you mentioned, which are saturation and cut off. But low power electronics use the region between these two, and there's still reverse saturation and others to think about.

If you are designing digital electronics, then maybe these are the only two states you use, but there are many more states to choose from.

It isn't just "low power" electronics that run MOSFETs in linear mode. I have designed more than one MOSFET based linear regulator.

MOSFETs have the advantage of not having a 2nd breakdown so you get more time to shut them down in the overload case.