If you have gotten rid of the standard THD rise at 6kHz (or so) and dare to present wide(er) band measurements without the standard HF filter - and it still looks OK - please step forward! The world needs you!
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I loved it - if not for the exquisite use of language, semantic foray, high spirit and grit. If it is correct or not I have no clue :-D
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But then it's not impedance.
Too many folks simply plot the magnitude of the impedance and label it "R" Ohms.Arrrgh!
What we agree about is the whole Middlebrook thing.
In the Post 1028 Sim, I showed that ic/vbe is distinctly different from IC(DC) q / (k T) = transconductance gm. If Early does not explain this, what does?
Your sim does not even include transistors or a transistor small signal model. How could it possibly detect Early?
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So I read your article on CFA's and about the author. So is it Lithium or Apo-Quatiapine? My brother an I are on differing medications.
So now we have several people who actually agree on the principle but still argue, and one so frustrated he resorts to personal attacks. I am almost done with my dissertation on Group Dynamics
@Scott: opened up the SYS2722 and what do you know; as if Santa emptied a bag of 797's in the thing!
Jan
@Scott: opened up the SYS2722 and what do you know; as if Santa emptied a bag of 797's in the thing!
Jan
Well that's another misunderstanding, your complete diagram of posting #1028 was used as a subckt as well as a version where Q1 to Q4 are replaced by ideal transistors shunted with parametrised Early Effect resistors.
Hans
So now we have several people who actually agree on the principle but still argue, and one so frustrated he resorts to personal attacks. I am almost done with my dissertation on Group Dynamics
@Scott: opened up the SYS2722 and what do you know; as if Santa emptied a bag of 797's in the thing!
Jan
Of course Bruce and I are good buddies, our sound group gets like SN 2 or 3 on every new box.
@CPaul - just to stay OT, you said 4.5pF and 200M Ohms for the AD846. That's about a 180Hz corner so by a few 100Hz it is pure transconductance.
The sim I sent used the spice models for 2N3904 and '06. And when I ran the sim Scott sent with Bob Cordell's transistor models, I saw the same thing: gm unequal to ic/vbe.
Then in a later post, I derived the Early effect using the small signal Hybrid Pi model. The results were NOT dependent on any specific operating point.
It is sometimes as if you are talking like the Oracle of Delphi, it can mean anything or nothing.
Are you trying to say that my 2N3906 and 06 are different from yours, come on. That's just another wild guess, after first having said that I didn't even use real transistors.
Previously I checked all your information in tables in #1028 and I had exactly the same results as you did. Conclusion, we are using the same data.
Just admit for once and for all that the Early effect has a an influence on the working of the CFA that can be totally neglected and we can close that book, there's no excuse left.
When Scott and my Sims can't convince you, you're lost.
Hans
The 4.5pF is from the data sheet. I don't dispute, but don't recall citing, the 200Mohm. Your calculation is true for the current mirror transistors Q14 and Q16, but not for the input transistors Q6 and Q12, which is what I have been discussing all along.
My claim refers to the relative importance of two mechanisms in the input transistors: Early and transconductance.
I would appreciate you addressing an observation: why, in both of our simulations, is ic/vbe so different from I(DC) q / (k T)? I don't believe I ever got an explanation for this from you.
Obviously, I found this at specific operating points. But if you know of some reason to expect these parameters to be equal at other operating points, please advise me of it. And even if that reason exists, if it is true at randomly chosen points in both my and your simulations, should it not be considered to be of some significance?
Finally, if the transistor spice models are not to be accepted as reasonably accurate in this sense, then we shouldn't waste our time with any transistor simulations.
Boy, are we miscommunicating! When I opened your sim, I didn't see transistors. I saw ideal sources. Which sims/results are you talking about?
Excellent. You replicated my results. So why is ic/vbe different from I q / (k T)? I cannot seem to get anyone to answer this simple question, despite asking it repeatedly.
Tremendous miscommunication again! Its not that I dispute your results, I just don't see any relevance to the question of Early vs. transconductance.
I ask again for the umpteenth time: Why is ic/vbe different from I q / (k T)?
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#1276, using the subckts from #1289, resp CFA3604 and CFA-Ideal.
The wording Ideal has only to do with the Q1-Q4 as you can see and nothing with an Ideal CFA.
You gave the answer yourself and I checked that it was indeed the Early effect with an Ro of circa 140K. End of the story.
My sims as used in #1276 are showing that Gain Z(s)/Rf with an Rf of 1K is going from 44.77@Ro=140K to 45.09@Ro=70k, so only a very minor 0.7% effect in gain from one to another just meaningless gain figure.
Only when Ro gets a ridiculous value below 10k, it starts to hamper the CFA in its role as CFA.
A gain changing effect can also be found with the model in #1276 when (slightly) changing the input resistance of the inverting input, thereby decreasing the gain.
Hans
Maybe... I only use Ad hominem arguments on my friends... and only under special circumstances I can't otherwise win. I am still working to clarify a response to the questions you asked specific to current reversal.
Maybe not quite the end of story, but real progress! Please read on.
I have never claimed that the Early effect significantly affected loop gain. Never! Where do you get this stuff from?
What I claimed is that vbe was reduced so much by loop gain that the Ro current became significant in comparison to vbe gm. And for this reason, the transistor was acting as anything but an ideal transconductor. In conclusion, this has even more adverse consequences for the "only voltage feedback, never current feedback" argument.
We are having a miscommunication here. This is more and more apparent as you keep making adamant points about things that I have never disagreed with and still don't. Kindly maintain some respect and refrain from ad hominems comparing me to historical mystics or those who are in desperate need of a GPS, and I will accord you the same respect.