Steve said
>The 5400pF is measured at 1MHz, but it's not going to change that much
at other frequencies, and at the upper end of hf Zi looks like a half
decent short circuit. Maybe matching at the top end and then frequency
tailoring an input attenuator will work.<
I make the input impedance of the order of -j0.9 at 30MHz. To get the power, I
reckon the drain to drain load is around 50 ohms, and that means quite a few
amps of drain current. Even if gm was 1A/V, that's a fair amount of RF base
current, and probable loss in the input matching network.
Question: if you take the Tchebyscheff filter variant that runs from 1 ohm to
an open circuit, how much does it degrade if the open circuit is say 200 ohms
i.e. an impedance ratio of 200:1? And how good is the match, supposing you
designed it for a 1 ohm to 200 ohms? (Don't have my copy of Zverev with me at
the moment)
Looking at possibly a straight match to 2 ohms, using a filter, it looks
possible, although you might need a lot of drive to get the volts across the
load resistor. You'd then need a wide band 50 to 2 ohm xfmr.
Steve, what are the chances of running in grounded gate?
73
Peter G3RZP
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