... and no source resistors for paralleled IRF240/9240 devices. Sorry John, this is not any real world amplifier.
Yeah I see that, but it's just a tone with it's 3rd harmonic in phase. So, no phase shift, no modulation (unless you call harmonic distortion 'gain modulation' which I can also agree to).
Sorry I came here late and am trying to find out what the issue is.
jd
it can work without source resistance, but only with hitachi
devices, 2SJ50/2SK135 or the TOP3 variants 2SJ162/2SK1058,
provided they are very well matched, as the point of thermal
indifference is at 100 mA for these devices..
still, in my design, they are always presents...
with IRFs, it s hopeless, and even dangeourous...
I agree, but he builds it with IRF240/9240. That's why Upupa, me and others do not believe it is a real, usable thing.
We don't need instruction manual, Federmann...you don't have still functional sample...
And don't forget my first questions - which load, which voltage...
And don't forget my first questions - which load, which voltage...
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No help for current distribution between such dissimilar devices as IRFs. These are not Sanken BJTs.
Image does not show the phase angle, the image does not show modulation. Picture shows Vdif and when Vdif reaches the nonlinear region. Non-linear ways of modulation.
The topic is about something else when the results of measurements HQQF completed, and will set a new thread, it is premature to put out the hasty conclusions.
federmann, as aknowledged by your site, you look to be someone
very intelligent, but it s useless re inventing what is already a norm..
i invite you to take some inspirations from renowed designers, you
will spare yourself a lot of waste of time and money...
all the best,
wahab
HQQF bandwidth is 4 times larger than the bandwidth QQF, but everything is still only approximate.
Not sure I follow you here. Yes, there is a phase shift between input and output. That phaseshift increases with frequency. So the input signal, and the feedback signal are increasingly out of phase with increasing frequency.
Therefor, the feedback no longer exactly cancels the fraction of the output signal with the input signal, there is an increasing Vdiff (=Vin-Vfeedback) and distortion rises with frequency because feedback is increasingly ineffective. That's how feedback works.
BUT the distortion component, which is generated by the forward path, shown in your graph, is exactly in phase with the input signal. So I don't see what else there is except plain harmonic distortion. And yes, that is a form of amplitude modulation.
jd
I went to School of Hard Knox.
There are all sorts of things that cause phase shift. The most common is frequency response irregularities- in a minimum phase system, phase is the derivative of amplitude versus frequency even if the transfer function is linear with amplitude. And there's all-pass filters for those who like non-minimum phase.
There is some use of the term 'linear distortion' for freq response and phase response irregularities, versus 'non-linear distortion' for harmonic component generations.
Not everybody agrees to this distinction, but ist is usefull because it shows that the mechanisms are not always the same. Phase shifts do not cause new harmonics, but non-linearities do.
Also, even in a perfectly linear system, without any harmonics, freq response roll-off causes phase shifts.
jd
Two topology, 100kHz to see when it will Vdif in non-linear region.
Amplification without feedback
Output Phase
Vdif
Amplification without feedback
Output Phase
Vdif
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