[Amps] Advanced Power Technologies ARF1505

[Peter Chadwick]

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