It's really tricky to do a frequency domain analysis on a waveform as
distorted as the one appearing on a class C amplifier collector. Unless
you're extremely careful and very aware of exactly what you're doing,
results are likely to be very wrong. Among other things, you have to
rigorously preserve phase information for each frequency. I personally
think a time domain approach is much more likely to yield correct
results, and this has been done. Search for papers by Sokal and Sokal
about class E amplifiers. I believe Frederick Raab did a lot of the
mathematical analysis, and published a number of papers on the topic.
I'd be very skeptical of any frequency domain analysis, or even general
intuitive arguments based solely on frequency domain considerations.

You'll probably find more references on class E amplifiers in
_Experimental Methods_. Class E amplifiers are essentially class C
amplifiers in which the output networks are carefully and rigorously
designed (using time domain techniques) to maximize efficiency.

Roy Lewallen, W7EL

Mike Silva wrote:
wrote in message . ..

It seems that the formula should be adjusted to account
for the conduction angle, e.g. Rl should be smaller by at
least a factor of 2 to compensate for the conduction
angle. What am I missing?

More current is flowing thru the transistor when conducting than would normally
be used if class-A ? ... this would average out because it's being pulsed rather
than continuous.


And it's reasonable to expect higher current in the pulse than Ohm's
Law would give, because the pulse has a whole bunch of energy in
harmonics, for which the load impedance is lower (the load C reactance
being lower). Since the harmonic content of the pulse goes up as the
conduction angle gets smaller, it makes sense that the average current
through the whole cycle would be somewhat independent of conduction
angle.

Just don't ask me to prove it! ;-)

73,
Mike, KK6GM