On Tue, 13 Sep 2005 20:33:11 -0700, "Jim"
wrote:

Most power MosFets have a large Gate to Source capacitance which makes it
difficult to use them at radio frequencies.

It can be done, but the higher the desired operating frequency the
greater effect the parasitic capacitance has, so most designs I have seen
were up to 7 MHz and that was about the upper limit.



Jim Pennell
N6BIU

7mhz was not the upper limit but around 20m the Gate Xc does makes
them harder to drive.

There are a number of designs that run them as linear amps to 10m but
the drive networks take that into account. A pair of IRF510s will do
35-40W in the FARA design published in QST.

Allison