Well, according to the datasheet:
Input C 180 pF
Output C 81 PF
Reverse transfer C 15 pF.
So if we drive the gate, we have 180 +15(1+Av) pF
Av being the voltage gain.
If we drive the source, we have 180 + 81 pF so depending on the gain, the input capacitance is not hugely different in either configuration. However, you have the same current in the source as in the drain, so you need to supply all the current from the driver that appears in the output. Its much easier to drive the gate then the source. So Allison is correct in that the impedance would need to be very low, a step down transformer would be needed to drive the source and still a lot of current would be needed to drive the transformer. Pick your poison. I like the grounded source better.
Quoting Howard Fidel <sonic1@...>:
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Yes, but there is no Miller capacitance so the total is less.
Quoting Brian <vk4bap@...>:
Is the reason for not using power MOSFET's in grounded gate the high drain-source capacitance? Looking at the IRF510 datasheet it looks like drain-source capacitance is higher than gate-source. Have I read that correctly?
Brian VK4BAP
