Well, that seems to nail down the history. I'm surprised Bob and Edmond haven't commented.
It seems a bit odd that such a useful technique slid into total obscurity before being re-invented a few decades later. I guess it would have helped if they'd given the patent a more imaginative title than "MULTISTAGE AMPLIFIER CIRCUIT".
On the up-side the patent's thoroughly expired, so the IP should be public domain now (ignoring the idiots who re-patented the same thing a few years ago, and whose "preferred embodiments" were so badly flawed they wouldn't actually work).
But that negative resistance is a function of feedback (again, often within a single device), so I think I'll stick to my semantic view.
Feedback is feedback, whether as an explicit loop, unintended coupling, or intentional degeneration/regeneration. It exists in every real world circuit, regardless of the "philosophy" of the "designer." (Rule of thumb: avoid any box of gain designed by someone with a philosophy. Remember what Masha said to Max Renn in Videodrome.)
Exactly! Nothing more and nothing less.
BTW, what's the difference between parasitic- and non-parasitic oscillations?
Let me guess: parasitic oscillation is the unexpected result of a negligently and carelessly designed amp for which the designer has no clear cut explanation. And what are non-parasitic oscillations? Comments invited.
Cheers,
E.
Yes, I do have your book. I've downloaded it, so I've paid the right price for it....
Very considerate, Edmond
. But why would anybody expect anything better from you?I'd say parasitic oscillations are the ones caused by "components" not shown on the circuit diagram e.g. stray capacitance and lead inductance. I think "unexpected result of a negligently and carelessly designed amp" applies to both parasitic- and non-parasitic oscillations.
Oh, right - I missed that at the time. IMHO you summed up the state of the US patent industry quite nicely here too.
>I'd say parasitic oscillations are the ones caused by "components" not shown on the circuit diagram e.g. stray capacitance and lead inductance.
Now suppose that some one more 'skilled in the art' includes these 'invisible components' into his schematic and/or simulation. IOW, they become 'real' components. Also suppose that the simulation reveals instability. Do we still call this 'parasitic' or 'non-parasitic' instability or should we say the frequency compensation is just inadequate.
I vote for the latter, as those 'invisible components' count just as much as all other components. Have look at PCB of a motherboard, for example, and you will see zigzag traces which equalize delay times. To me, they should be considered as real components. If that being the case, it makes less sense to distinguish between stray and non-stray inductances respectively capacitances.
Cheers,
E.
Now suppose that some one more 'skilled in the art' includes these 'invisible components' into his schematic and/or simulation. IOW, they become 'real' components. Also suppose that the simulation reveals instability. Do we still call this 'parasitic' or 'non-parasitic' instability or should we say the frequency compensation is just inadequate.
I vote for the latter, as those 'invisible components' count just as much as all other components. Have look at PCB of a motherboard, for example, and you will see zigzag traces which equalize delay times. To me, they should be considered as real components. If that being the case, it makes less sense to distinguish between stray and non-stray inductances respectively capacitances.
Cheers,
E.
It has been pointed out several times now that so far as anyone knows, the original inventor was Kunio Seki, in 1978; see US Patent 4,145,666 assigned to Hitachi. Unlike some people, I have never at any point claimed I invented it, re-invented it, popularised it, or done anything with it except use the information passed on to me by Peter Baxandall. I may however be the only person in this discussion who has actually made money out of it.
In your 600 page book, you only referenced my work five times.
(For those not in the know, this diagram shows the very large currents that can be drawn by a loudspeaker if you hit it with a carefully designed set of pulses)
I gather that you published your version in 1983. I am not aware of this publication; perhaps you could enlighten us.
My diagram was directly inspired by the well-known but fallacious paper by Otala et al: "Peak Current Requirement of Commercial Loudspeaker Systems" JAES Volume 35 Issue 6 pp455-462; June 1987. It is of course of little more than curiosity value as the irregular square waves that are required to show the effect do not exist in music.
My diagram first appeared in the very collectable Second edition of Audio Power Amplifier Design, in 2000. That is a long time to harbouri a grievance.
It is probably a bit hard for them when any comment will attract criticism that they harp on about it.
So to leave them the time to reply to my queries
I'll do it.The response here doesn't indicate any reluctance to admit priority, or quibble.
Now can we discuss actual solid state technical issues?
Best wishes
David
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Oh really?
What about this post: http://www.diyaudio.com/forums/soli...terview-negative-feedback-76.html#post1168039 :
Quote:
Originally posted by mikeks
Who invented this exercise in futility then and what did they call it?
Hi Bob and Mike,
As far as I know this "exercise in futility" (not my words) was first invented by the late P. Baxandall, then re-invented by D. Self (according to private communications with D.Self and me). Then we have Lars Clausen, see post #512, who essentially applied the same technique. Regrettably, I don't have any paper on this subject, so I don't know how the original inventor might have called it, hence my suggestion to call it TMC.
And in your 583 page book, you only referenced Bob's work two times.
So, what your point?
The global feedback loop has a completely different delay/freqency/pole as a single part with parasitic oscillation. So for me a working and Miller compensated amplifier (audio range gain ok ...) can have extremly high parasitic oscillation - and therefore sounds really bad or simply breaks.
If we now add a stopper resistor to avoid local parasitic oscillation IMHO has nothing to do with the compensation of the feedback loop. I would not say that this is part of the "Miller compensation". Mathematically it has nothing to do with it. I completely agree with Douglas.
Cheers Toni
If we now add a stopper resistor to avoid local parasitic oscillation IMHO has nothing to do with the compensation of the feedback loop. I would not say that this is part of the "Miller compensation". Mathematically it has nothing to do with it. I completely agree with Douglas.
Cheers Toni
Even considering the first is published since nineties and the later is in its first edition, from few years ago?
BTW, both are very good books, IMHO.
Regards,
and JLH's + Cordell's + Self's are all worth having on the shelf for reference.
They each handle their topics in their ways and it's useful to see how this helps with (my) understanding.
I do look forward to seeing Self's 6th. My copy is 2nd, with 4th add ins, and quite a few topics did need considerable expansion.
They each handle their topics in their ways and it's useful to see how this helps with (my) understanding.
I do look forward to seeing Self's 6th. My copy is 2nd, with 4th add ins, and quite a few topics did need considerable expansion.
That's a lot for a book that was at the time still in the author's drawer/head.
Both books are, to me, excellent. I though value more "depth" over "width".
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Can we please stop the silly argument about who did what? If we are presenting a Phd thesis then perhaps you would need to site all appropriate reference material to the paper but these are technical books written from the authors point of view and preferred circuit design topologies. Otherwise you all have to start at say a Marconi or Edison and Tesla and show who invented ac and dc and start from there in giving credits! So much of what you are talking about was done on a lessor basis in vacuum tube designs that I think we should just drop it and if the authors want to acknowledge another engineer that is their prerogative to do. If you only want to give credit to your wife or your dog, that shouldn't change the tone of the book or the quality of the writing.
Let's get back to what we want to see in a next addition. Perhaps since each author has different approaches to these subjects they can agree between themselves to divide up the subject into each persons personal design intention going forward.
Let's get back to what we want to see in a next addition. Perhaps since each author has different approaches to these subjects they can agree between themselves to divide up the subject into each persons personal design intention going forward.
Hi Toni,
Please, don't forget that that Miller thingy is a feedback loop in his own right. As with all FB loops, also this one must be kept stable, basically with the same arsenal of tricks which makes a global FB loop stable. You are right, it's no part of the Miller compensation, instead, it's a compensation of the Miller FB loop.
But... that doesn't mean Douglas is right. He said the 33pF caps in Cherry's amp are not meant as shunt compensation. However, the question is: shunt compensation of what? Global FB compensation? No! Local (i.e. Miller) loop compensation? Yes!
Cheers,
E.
BTW, here's one more chap who (re)invented TMC: Lars Clausen.
See: http://www.diyaudio.com/forums/soli...terview-negative-feedback-52.html#post1160451
Does anybody know when he invented this?
See: http://www.diyaudio.com/forums/soli...terview-negative-feedback-52.html#post1160451
Does anybody know when he invented this?
I think it was always in obscurity, not that it slid into it. The patent title is an obvious attempt at concealment, as is not uncommon in the business. They would have called it "ELECTRIC CIRCUIT" if they could have got away with it.
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