Tony wrote, "... a function of the source impedance. Since this is never specified, ...".
Sometimes it is.? There might be s parameters, or an output port reflection coefficient, or something like that.? But you're right, it is often not specified.
I guess it might depend on the market into which the RF amplifier is being sold.? There are applications for which knowing the output's source impedance (or the goodness of that match) is quite important, and so they have a datasheet spec for it.
Andy
