On Jun 6, 3:21*pm, Wimpie wrote:

Measuring method used: change in resistive load, from voltage change
you can calculate the current change, hence the output impedance. One
note, except two, all where solid state.

Of course, since the source impedance may be anywhere in the complex
plane, you need to change more than just the resistive part of the
load, I believe, to get an accurate picture...

All high efficiency designs (class E, D) that I did have output
impedance far from the expected load impedance. With "far" I mean
factor 2 or factor 0.5. I did not measure that (as it is not
important in virtually all cases), but know it from the overload
simulation/measurement and I did the design myself.

What I've seen in similar situations is that the source impedance is
likely to be strongly reactive, depending on the filter network you
use to get sinusoidal output. In any event, the source impedance is
likely to have a reflection coefficient magnitude that is quite close
to unity. That is exactly what you should expect: there's nothing to
absorb reflections. You could (theoretically at least) use feedback
to make the output look like 50 ohms, but just as you say, Wim ...
why?? There's really almost never any point in doing so.

....


Cheers,
Tom