mrf150 amplifiers

The MRF150 is frequently used for HF amplifiers.

I think I should clarify my question. I would like to know what is the criteria for choosing a transistor for class E PA design. Because the transistor is considered as a switch, any consideration should be made for this condition in the transistor selection, e.g. ft or gain?

What is not critical is output capacitance. This is taken advantage of by the output network. Switching speed and Ft are important and should be high.

Output capacitance IS critical. You can always add more (externally) in order to reach a required value. The required value will depend on the frequency of operation, the supply voltage and the desired output power.