Hi Ian.
> In other words, the thing that we carelessly call "output impedance" for
> design purposes is purely FICTIONAL. I think that's why Tom calls it
> "non-dissipative" - because it doesn't actually exist.
It certainly does exist, and it can be measured with simple
equipment.
> The true (and therefore dissipative) output impedance of the device is
> usually much lower than the optimum load impedance, which is what allows
> efficiencies greater than 50%.
Viewed from the output terminals, over 15 PA's tested all produced
maximum power and efficiency for a given amout of drive when
conjuagately matched. That means either a load pull, or excitation
by a reverse power generator near the operating frequency, indicated
the PA behaved as if the source impedance was the complex conjugate
of the load impedance.
It is an actual impedance with a real part, but the real part is not
dissipative.
73, Tom W8JI
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