To be deleted

[Turbo]

There is a function called Sound_Play() in mikroC library and i have had success with that.
The Prototype is void Sound_Play(unsigned freq_in_hz, unsigned duration_ms);
https://download.mikroe.com/documents/compilers/mikroc/pic/help/sound_library.htm
So you can easily pass frequency and duration as parameters and so you can roll your own function that incorporates the mark duration, as well as delay for the space duration.

If you need higher frequency's you have to switch to classic PWM.
But who does not remember being a child and hearing the 20K whistle coming from the CRT Flyback tv when we was young ? _{and the resulting crackle from the electrostatic field on the tube when touched...}
Of course now i'm old and i can't hear that high no more.

[nul-points]

time to recap on the original circuit we're looking at here (and which Itsu is kindly looking at replicating)

i'm attaching an overview of the circuit - it has 1 supply branch and effectively 2 branches (ignoring a higher impedance biasing branch with an effective impedance of approx 10k ohm at 130kHz)

one branch is entirely a current drain, Iin, on the supply and the other is entirely feeding current, Ifb, back to the supply

the net supply current, Isupply, is Iin - Ifb


np

[Void]

Hi Void,
on this wiki there is some info on rms values / waveform:
https://en.wikipedia.org/wiki/Crest_factor
So every waveform needs its specific calculation to arrive at the correct rms value.
I can not see how a scope does that, so probably there is some generic way.
But i agree, (power) measurements are no easy task and marginal cop > 1 values should be treated with causion.
Itsu

Hi Itsu. I think the way a scope does it may be as follows:
The way a scope calculates RMS values is to square all the measured sample values taken over a period of time,
then calculate the mean of those squared values, and then take the square root of the calculated mean.
It's been a long time since I studied such things, but I think this may be how it is done in scopes (or similar).
As my scope's manual states: "RMS: Root mean square of all data values." 

Your measurements so far are showing a fair bit of variation, so not so super reliable, possibly because
the circuit is not so stable, but likely at least in part due to the current probe not giving highly
accurate measurements at those low current levels. Still it seems pretty clear already that there is no
indication of OU in that circuit arrangement when measurements are done properly.

[Void]

time to recap on the original circuit we're looking at here (and which Itsu is kindly looking at replicating)
i'm attaching an overview of the circuit - it has 1 supply branch and effectively 2 branches (ignoring a higher impedance biasing branch with an effective impedance of approx 10k ohm at 130kHz)
one branch is entirely a current drain, Iin, on the supply and the other is entirely feeding current, Ifb, back to the supply
the net supply current, Isupply, is Iin - Ifb
np

Hi Nul-points. Although Itsu's measurements are not showing as super consistent/accurate,
which may possibly be partly due to circuit instability and very possibly/likely an accuracy limitation of his
current probe at low currents, the measurement method Itsu is using appears to be correct (and it passes sanity checks), 
so Itsu's measurements should be close enough for general analysis purposes, so it should be pretty clear by now
that there are so far no signs of OU in your circuit arrangement.

My recent comments have been to demonstrate how tricky it can be to make really accurate measurements
on circuits that contain complex AC waveforms, and how important it therefore is to question and examine everything
very closely to see where a person might possibly be going wrong or overlooking something in their measurements.
Nul-points, you seem to have ignored this, and also ignored that your previous measurements and calculations
are way off compared to what Itsu has been measuring using an (apparently) correct measurement method (although
apparently not so super accurate with Itsu's current probe). Nul-points, what do you think about this? Do you acknowledge
that Itsu's measurement approach is correct, even if it may not be super accurate/consistent when using his current probe?
If you don't think Itsu's measurement approach is correct, please explain why.

P.S. Regarding your latest drawing posted above, efficiency is calculated as a ratio of average power out to average power in,
so you taking a ratio of currents is completely wrong. You also seem to be trying to analyze the circuit as if it is some
sort of DC circuit or simple AC circuit, which is not correct, as the circuit produces complex AC waveforms, and I have already
gone into much detail in this thread to demonstrate and explain what to watch out for and how to make proper measurements
in that type of circuit, and showed possible ways to do a sanity check on measurements to make sure the measurements are
reasonably in the ballpark of what should be expected. As best as I can tell, Itsu's measurement approach is correct, and is not
showing any signs of OU.

[Void]

But i agree, (power) measurements are no easy task and marginal cop > 1 values should be treated with causion.

This bears repeating. At low power levels such as in the low mW or lower, 
a difference in measurement of even several mW can be well within the margin of measurement error,
so, yes, I would say jumping to conclusions when measuring on AC circuits with complex waveforms
at low power levels is not at all a good idea. There is just too much room for error or oversights there.

Now, if a person can scale up their circuit to much higher power levels and still measure a higher average
output power than average input power with a difference in the order of many Watts, then IMO that would bear a
much closer look, assuming the measurement methods stand up to close examination. The easiest of all is
just to self-loop a circuit and see if you can get it to self-sustain, as that way no measurements are required.