IRF510 amplifier failures

Arv Evans
 

Hello

The problem with IRF510 RF amplifiers failing seems to be a recurring one for those who
are not quite careful with antenna matching, bias level, and drive level.  As a way to start
looking into this situation I have performed some on-line searches to see how others are
And there is much more out there to be Google searched and reviewed.

There are a number of potentially useful ideas contained in those articles and discussions,
but nothing that obviously applies directly to the problem of blowing IRF510 devices at only
a few watts of power if the antenna is mis-matched.  Mention of using small resistance values
in series with gate drive is interesting, as is use of pi-net attenuators between exciter and
RF PA gate...to help control impedance?  While we look upon the MOSFET internal capacitance
as being a problem, it is interesting that some designs add a capacitor on the drain side of
things, apparently to limit the upper frequency capability and reduce 'spikes'.  The discussion
on single-ended versus push-pull is interesting from a technical view, but did not introduce
anything obvious that could help.

I suppose we have to first determine just what the exact cause of IRF510 failure might be,
then use that as the basis for designing a suitable solution.

Arv  K7HKL
_._




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