> From: Gregg Kricorissian <grkricor@ccs.carleton.ca>
> [lots of good stuff snipped]

I would recommend the book 'Power Electronics' by B.W.Williams (McMillan)
as an excellent reference on this type of stuff.

Gregg stated a Rds(on) coefficient of +0.6%/K hovever said reference indicated
only +0.1%/K.  Never mind, but I would be interested in knowing the tempco
of the threshold voltage since this is not mentioned, and could be an
important consideration in paralleling mosfets especially if the gate
driver has trouble pushing all the capacitance.  (Currently I'm designing
a 2KW 20KV HF AC supply for running my laser tube - PIC controlled, of
course, so hopefully Jory won't zap me for digressing!).

A good trick for current sharing two devices is


         ---+----
            |
            -
           | | load
           | |
            -
            |
            |
         ---+---
         |     |
         3 | | 3 o
         3 | | 3
       o 3 | | 3
         |     |
         |     |
       |-    |-
      ||    ||
       |-    |-
         |     |
         |     |
       --+-----+---

The funny thing with '3's is supposed to be a transformer with
windings as shown, tightly coupled as per bifilar wound toroid.
Any tendency for one device to draw higher current causes a higher
voltage to be impressed on the other device, forcing the latter
device to take its fair share.

This works with switching designs only.  The transformer core must not
saturate from prolonged imbalance.  This design is much more efficient
than the usual resistors.

Regards,
SJH
Canberra, Australia