On 7/10/05, Olin Lathrop <olin_piclist@embedinc.com> wrote:

> However, rethinking the circuit topology is in order.  Why are you using a
> FET in the first place?  Bipolar transistors operate on current.  The
> control circuit for a bipolar will have to do less "work" to maintain
> constant current thru the collector.  In other words, bipolars are
> inherently more stable when used as current sinks.

I'm only using FETs as I have them here on hand and i'm not averse to
using BJTs, but I can't see what this extra "work" is?

> You're also going to have a problem of power dissipation.  You are talking
> about sinking up to 450 watts.  That's a lot more than a single transistor

Yes, I understand that. At the moment i'm just trying with a single
transistor with a load of a couple of amps to get the thing going. I
would then replicate that the required number of times to cater for
full power.

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