Be careful!
The spec for Vgs to 20v. is for putting the device in the "full on"
condition. At 0v the switch is "full off", but at some gate voltage
(usually around 5v) it turns rather suddenly to "full on".
Remember, these are really electronic switches.
You are looking for the linear region between these conditions.
It is small but it is effective for RF. Usually that is a gate voltage
of 3-4v, no matter what the RF signal frequency is.
So START at 0v. on the gate and work up from there. Try to
avoid too high a gate voltage as it will fry the MOSFET in an
instant.
The real secret, I suppose, to matching a MOSFET to RF is
handling the gate capacitance at a given frequency range.
Layout is important. So is input impedance. So is heat
transfer.
john
AD5YE
