[Amps] Direct rectification of AC mains to drive the amp, VDD Supply

[Bill Turner]

ORIGINAL MESSAGE:          (may be snipped)

On Mon, 23 Sep 2013 16:07:13 +0000, you wrote:

>Now the question is if these specific MOSFETs can actually work at 
>300-350VDC in linear class AB, close to their full ratings, without 
>having this trouble. I have read some papers telling that they cannot, 
>but I have never tried it muyself - they are too expensive to fry them!
>
>If anybody here has actually used them in linear service at 300V or 
>more, and high power, for a prolongued time without failures, I would 
>absolutely love to hear about it! If nobody has done it, the first who 
>does will be wading uncharted territory.

REPLY:

Hi Manfred:  If this hotspotting problem occurs, say when doing RTTY at a
high power level, how quickly does it happen? For example, if one is
watching the drain current, would one see a gradual increase or a sudden
catastrophic one? 

Also, could this be tested with only DC? If one ramps up the bias with DC
only to where the push pull pair is dissipating 1500 watts without
hotspotting, could one be confident they would be safe doing RF?

73, Bill W6WRT