It is too noisy, Bob. It would change 1nV/rt Hz to 3nV/rt Hz minimum. What about jfets? Of course, this is why Scott did not degenerate his input stage in the AD797.
I've read through Charles' long post. I still feel that 'intrinsic feedback' as a name for degeneration would be almost as misleading as calling it 'no feedback'. Two big differences between the internal and external resistances are that only the external one actually exists (the internal one is just a way of modelling the device in the immediate vicinity of the bias point) and the internal one is very non-linear. I would be happy to call it 'local feedback' or (my suggestion) 'intra-stage feedback', but I have no problem with 'degeneration'.
Built-in emitter resistors are not that rare. You can find them in many RF power transistors.
Built-in emitter resistors are not that rare. You can find them in many RF power transistors.
Sanyo B817/D1047, a single ballast resistor, something like 0.05-0.07R, still RE
(for LAPTs, the total equivalent resistance likely becomes negligible)
(for LAPTs, the total equivalent resistance likely becomes negligible)
Intrinsic means "belonging to the essential nature or constitution of a thing" The thing in this case is a gain stage.
No, the 'thing' is a transistor. The Re is in the transistor, whether it is used as a gain stage, a regulator or an oscillator. It's always there. 😉
jan
My suggestion of 'intra-stage feedback' probably comes from the same latin root, but makes it clear that we are talking about the stage not the device. 'Intrinsic' might have been OK if it was not already used in connection with devices. However, emitter degeneration definitely does not belong to the "essential nature or constitution" of the stage (except for a follower), as it can be present to varying degrees or absent.
I am still puzzled why people are so reluctant to simply call it local feedback. That is what it is. It is a perfectly accurate use of an existing term.
I am still puzzled why people are so reluctant to simply call it local feedback. That is what it is. It is a perfectly accurate use of an existing term.
"Intrinsic feedback" would also describe the Plate resistance of a tube,
and other dependencies of gain on the voltage across a device.
😎
and other dependencies of gain on the voltage across a device.
😎
For those interested in the recursive aspects of feedback, and who can get access to it (I can't), there *may* be something interesting in an article by R. Feldkeller in _Teleg. fernsp. Tech._ vol 25 p. 217, 1936. It's referenced in an old McGraw-Hill (ed. Terman) series _Electron-tube Circuits_, Seely 1950 p. 84 where he discusses the linearity assumptions in feedback equations. Long before Baxandall/ Putzeys, fersure.
I'm constantly re-surprised that most anything "modern" was known in the 1930's.
Thanks,
Chris
I'm constantly re-surprised that most anything "modern" was known in the 1930's.
Thanks,
Chris
Yes. We can talk about 'intrinsic plate resistance' (coming from the tube alone) and 'plate resistance' ('extrinsic plate resistance'?) (boosted by degeneration).
Every Ohm mattered. No useful degeneration would fit into the noise budget. BTW one thing overlooked by last weeks arguing is that the complimentary JFET input was current on demand, really a huge innovation. Slew current on demand makes a huge difference.
Well, Scott, that is why we did not deliberately add degeneration resistors to audio stages, back in the 1960's, until we read Otala's papers or perhaps Solomon.
To my view, the term "intrinsic feedback" has is no implication on the term used for un-bypassed emitter/source/cathode resistor. The former is inside the devices, an unavoidable integral part to those devices, while the later refers to a topology, or circuit element, which is external to those devices.
Almost on topic:
I am searching for a couple of IEEE documents:
Abramovitch, 'The outrigger: a prehistoric feedback mechanism', Proc. 42nd IEEE Conference on Decision and Control, Dec 2003, pp 2000-2009;
Edit: this article looks the same as this:
http://www.labs.agilent.com/personal/Danny_Abramovitch/pubs/outrigger_hist_mat3.pdf
Lepschy, Mian, Viaro, 'Feedback control in ancient water and mechanical clocks', IEEE Trans on Education, vol 35, no 1 Feb 1992 pp3-10;
Michel, A N, 'Stability: The common thread in the evolution of feedback control', IEEE Control Systems Magazine, vol 16, no 3, June 1996, pp 50-60;
Headrick, M V, 'Origin and evolution of the anchor clock escapement', IEEE Control Systems Magazine, Vol 22, no 2, April 2002, pp 41-52.
Edit: it appears that this article is available online at:
http://www.abbeyclock.com/anchor.html
Does anybody here have access to these papers for study purposes?
jan didden
I am searching for a couple of IEEE documents:
Abramovitch, 'The outrigger: a prehistoric feedback mechanism', Proc. 42nd IEEE Conference on Decision and Control, Dec 2003, pp 2000-2009;
Edit: this article looks the same as this:
http://www.labs.agilent.com/personal/Danny_Abramovitch/pubs/outrigger_hist_mat3.pdf
Lepschy, Mian, Viaro, 'Feedback control in ancient water and mechanical clocks', IEEE Trans on Education, vol 35, no 1 Feb 1992 pp3-10;
Michel, A N, 'Stability: The common thread in the evolution of feedback control', IEEE Control Systems Magazine, vol 16, no 3, June 1996, pp 50-60;
Headrick, M V, 'Origin and evolution of the anchor clock escapement', IEEE Control Systems Magazine, Vol 22, no 2, April 2002, pp 41-52.
Edit: it appears that this article is available online at:
http://www.abbeyclock.com/anchor.html
Does anybody here have access to these papers for study purposes?
jan didden
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Almost on your request 😀
http://www.uni-graz.at/exp2www/Physikgeschichte/Water%20Clocks.pdf
http://137.148.142.85/cactwiki/images/4/46/WaterclockESSAY.pdf
Chapter 2 http://www.ee.iitb.ac.in/student/~krishnans/latex/Krishnan_Seminar/report_draft.pdf
Strange but good http://www.nickols.us/TankThatFilledItself.pdf
Regards
George
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