Thanks, Tom. That cleared up a lot for me.
> By the way, output impedance of any linear PA is always higher than the
> load impedance. Otherwise the PA will flat top and be non-linear. That
> includes transistors.
The 1995 ARRL Handbook says basically the same thing, although somewhat
less clearly (p 13.3, ff). They say that a Class A amplifier operating with
a conjugate match has a theoretical output efficiency of 50%, but in
practice the efficiency has to be lowered by adjusting the load resistance
to minimize distortion and plate dissipation. They go on to say that this
works better in Class AB, B, and C amplifiers because optimizing the load
resistance doesn't lower efficiency as much.
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