question about PA design

I am curious what is the first thing to look at when designing a power amplifier at specific frequency, is it bias Vs Ft? Also, is that the same for all the class (A,AB,C,etc)?thx

I think the class can be answered from a simple wiki look up:
Well the first thing to look at is how to obtain the specific frequency as the input through filtering. Once that is done you proceed to start processing it through amplification. Keep in mind that amplification can cause distortion so you may have to amplify and filter in various stages. You also are going to want to use capacitors to need reduce the noise of the signal.

This is really a mundane reply but I hope it at least gets you thinking.

I am not quite understand what the first sentence mean. but anyway thx for the information.