Quote Originally Posted by The Master View Post
I had a look for that book. £48.45 on Amazon! It wants to be good for that price. Ill add it to my x-mas list
Obviously, not everything in that book applies, but the first bunch of chapters (i.e. 1/3 of the book) breaks down the basics of transistors/mosfets, and the bulk of the discrete components needed to put together a complete circuit. And it really helps to have a few examples of each laying around, along with some spare parts and a meter (and/or 'scope) to play with pieces/parts and see what actually happens in practice vs. just reading all about it.

The LEDs im looking at are 15 degrees i guess that puts them towards the dimmer end.
Not necessarily. Look at the datasheets for those LEDs, look at the distribution, then compare that LED with the cheaper and more expensive types.

If i only need 200mA now is it still better to use a mosfet instead of an NPN transistor? Yes i can use NPN now with these other LEDs
I think you're better off using a MOSFET over a BJT anyday. The 'bible' mentioned above shows why and I don't remember exactly why. But it's got something to do with the forward bias voltage. A BJT gets hot, forward bias voltage drops a smidge, current flow rises, BJT gets hotter, forward bias voltage drops a smidge, current flow rises, it's a nasty circle of death for the BJT. With a MOSFET, it effectively chokes itself when it gets hot. I don't remember the exact mechanism by which this happens, but it supposedly can 'save itself' in certain situation whereas a BJT would go up in smoke.