Hi all,

In the midst of my research for the topics in my RF
tutorial, I have found a question which really has me
stumped and for which I can't find any answers anywhere.

All the books on RF amplifier design say that class C
RF amps should be operated with the transistor going
fully between saturation and cutoff to maximize
efficiency. This makes sense to me because you don't
want the transistor conducting current AND having a
significant voltage drop at the same time.

What I don't understand, though, is this: when you
design a transistor saturated switching circuit, you
usually want to know the switching paramaters for the
transistor (Ton, Toff, etc.) Yet, whenever I look up
datasheets for RF power transistors intended for class
C operation, no such parameters are given.

What gives? How are you supposed to know if a given
transistor can handle class C operation at a given
frequency? I'm also puzzled as to why you never see
Shottkey-clamped transistors in class C RF amplifier
service, since that would surely allow class C
operation at higher frequencies, wouldn't it?

Thanks,

Sean

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