On 30 November 2018 at 12:58 N1BUG <[email protected]> wrote:


Yesterday I replaced FETs in my 2200 meter amplifier. Since the
FQA34N20 is long discontinued I had no choice but to make a
substitute. I chose the FQA32N20C because I know of one active
station using them in the same amplifier with success.

I notice drain ringing is significantly greater with the new FETs,
but maybe acceptable. I have little choice but to run the amp and
see how it goes.

I also notice the gate voltage decay takes about twice as long as
the old FETs. According to the data sheets, turn off fall time on
the 32N20C is almost twice that of the 34N20. I suppose that is what
I am seeing. I *guess* this may be related to increased ringing, as
it appears one side is not fully off as the other begins to switch on.

I would appreciate any comments or suggestions, including
suggestions for a FET which might leave a longer dead zone at the
phase transition. I'd think slow to turn on, fast to turn off would
be nice...

Alternatively, if anyone has a stash of FQA34N20 purchased from a
well respected vendor (old stock) and would be willing to sell some,
I may be interested. I've already tried some which originated from a
Chinese source and am not interested in going down that road again. :-)

73,
Paul N1BUG
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