aaron_do
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Hi,
treating the MOSFET's input as purely capacitive is only really adequate at low frequencies. At millimeter-wave frequencies, you need to keep in mind the gate resistance. If you treat the gate resistance and capacitance as being in series, then the maximum power to the gate resistance also results in the maximum voltage across the gate capacitance. Its a simplified model though. As gain is scarce at millimeter-wave frequencies, it may be better to do an actual impedance match since in theory you can get higher gain.
It also depends on the Q of the inductors and capacitors which you have to do the matching. For the specific kind of matching network you want to use, the network Q and the component Q, you may or may not see any benefit.
Last point is that even if you were to treat the input impedance as purely imaginary, the highest voltage gain is not achieved with an LC resonance. You can always get higher gain by using a step-up transformer. The tradeoff is typically bandwidth and whether or not its practical to implement.
regards, Aaron
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