It depends on the device - I use PointNine Technologies
devices at this power and over the frequency range without
any bother. Motorola and Philips UHF parts are dreadful in
comparison.
Agreed. Motorola and Phillips pioneered, but much of
the better recent developments have come from smaller companies either
in the RF business, or in the very high power/high frequency pulsed DC domain.
BTW does PointNine have a web presence?
The real problem I find is material to load the
transformers to get the inductance at 50MHz without loss at
500MHz.
Designing transformers for this range must be especially interesting. The curie
temps
must be amusingly high as you are going to have significant losses somewhere.
(By significant, I mean enough to heat the material appreciably).
>Higher impedance MOSFET devices are emerging (1000V VDS),
but they are frequency
>limited to about 100MHZ, and not capable of generating more
than 150W or so. It might
>be possible to combine these devices as the impedances are
high enough, but I have not
>tried this.
High voltage is not a universal cureall. True, the load
resistance goes up, but if the output capacitive reactance
doesn't go up at least as fast, the upper frequency limit
is reduced. In general, that tends to be the way things work
out.
Agreed again. Die designers are developing some interesting
workarounds to lower the capacitance's, but the voltage still
has to go up along with the capacitance going down to make
these things easier to work with.
I bet mine's bigger than yours :-) (Not necessarily
something to boast about)
You have probably been at it longer than I and I will catch you at some point;)
The original question of why isn't there such a beast for amateur application
is somewhat answered by my bag of slagged FETs. All but two of them were
bought by employers/clients.
73's,
George
K0IW
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