Harold Hallikainen wrote:
> Determine the
> maximum collector current (looks like 2A)

30W / 12V = 2.5A

> Most FETs can be driven to full on with +5V out of the PIC pin.

Most FETs require about 10V on the gate to reach full on.  If you want a
reasonably low on resistance with 5V gate drive, you need to find a FET that
is explicitly specified that way.  Many of these are called "logic level"
FETs.  They are intended to have satisfactory Rdson at 5V gate drive,
although they can usually do a little better with 10V.

As I said before, the IRFU3706 is a good fit here.  The maximum Rdson at
4.5V gate drive is 11mOhm.  Last time I bought some, they were $.57 each for
100 from Richardson Electronics.  Singles were only 8 cents more each.


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