Homebrew PCBs

Roy J. Tellason wrote:

> This is the second post I've seen so far that seems to suggest that it's okay 
> to rely on the internal diodes in mosfets.  The general consensus in other 
> lists seems to be that this is _not_ a real good idea...

It depends upon the design.  Certainly the intrinsic
diode isn't typically as well characterized as a
discrete diode (though I've seen exceptions to this)
nor typically as fast as schottky types.

But unless there is a overriding cost/performance
reason reason to add an external shunt diode the
intrinsic diode is often sufficient.

The energy being dissipated by any diode in an
inductive shunt role is going to be much less
than a diode used to free-wheel current in a
switching regulator application when the switch
device is off.  It is the latter case where the
total switch device package heat dissipation is
of consequence and indeed where external diodes
are routinely employed.

-- 
uhmgawa@...        www.gnu.org