At 03:39 PM 14/04/2011, you wrote:

>This is slightly off the original question, but what is better for this so=
rt
>of application, a MOSFET, or a bipolar transistor. Since as mentioned, FET=
's
>are designed more for fast switching and often to stay out of the linear
>area, would a big transistor be a better choice since they were probably
>designed to be in the linear region of operation? I have a bag full of TO-=
3
>cased units from old linear power supplies for instance. Would they be
>better?

Might well be.. you can probably get away with a couple devices
in parallel (with some care to make sure they share nicely- I'd
tend to control them individually with (say) 1/2 the current each.
You can reliably run real (metal) TO3s at least 25'C-50'C hotter
than most plastic packages.

One approach would be to make a sort of hybrid darlington with a
smallish n-channel MOSFET and an PNP BJT, which means that the
collector/drain current of the hybrid device equals almost exactly
the emitter current.

>Best regards.

Spehro Pefhany --"it's the network..."            "The Journey is the rewar=
d"
speff@interlog.com             Info for manufacturers: http://www.trexon.co=
m
Embedded software/hardware/analog  Info for designers:  http://www.speff.co=
m



--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.