below have two switching circuits and both have connect with the diodes, anyone can tell me which circuit snubber connection is correct?

 

I vote for the first. For P channel, the arrow points to the Source, which is positive. For N channel, the arrow points to the Drain, which is positive. The diodes have to be reverse biased.

Here is a good reference on snubbers. Most use a resistor-capacitor combination and not a simple diode.

http://www.cde.com/tech/design.pdf

John

 

I think second is correct one

 

I think second is correct one

Could you expand on or explain a little more why you believe the second circuit is correct? John

 

The 2nd circuit would sound like an M16A2 in "BURST" mode, as either the upper MOSFETS or the lower diodes popped in three rapid bangs.