Homebrew PCBs

On Tuesday 21 June 2005 03:49 pm, uhmgawa wrote:

> BTW the discussion of external suppression diodes for mosfets is likely moot
> for devices where an internal parasitic diode is present.  The main reason
> to add an external schottky in SMPS designs is that of efficiency as the
> voltage drop across the internal diode is typically greater than available
> via the external schottky.

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,  for a number of 
reasons.  One of those is that those internal diodes don't have very 
consistent characteristics,  and another is that they turn on too slow,  and 
turn off too slow,  which will tend to make the device run hot.  Since heat 
is an enemy of semiconductors,  I'd tend to go with the external diodes,  
myself.