Clearly, but also mostly incorrect.
Comparing Miller (single pole) with TPC, TMC (two poles) is not apple to apple, so you can't say that Miller is suboptimal. Bananas are sweeter than apples, this doesn't make apples "suboptimal sweet". MIC is first order compensation, but it is... Miller by all means.
TPC, TMC and MIC do not, per se, allow higher slew rates. Once and forever, SR is a nonlinear large, signal effect, where the input stage saturates and the compensation cap is charged by whatever current is available (tail current for the standard long tail pair input stage VFAs, the feedback network current for the CFAs).
The comment about the "higher ULGFs observed in CFAs" is. The regular CFA topology trades open loop gain for bandwidth, practically because the input stage has unity gain (instead of a transconductance gain, like in VFAs) and, being an emitter follower, has a large bandwidth.
Nevertheless, the open loop gain-bandwidth product is about the same as in a VFA. To add insult to injury, as long as the OPS is ultimately limiting the open loop bandwidth (and the total phase shift), increasing the ULGF always reduces the stability margins, CFA or VFA, doesn't matter.
Invoking "minimum phase" doesn't have any sense in this context.
Because you mentioned stability in capacitive loads, all CFAs that I've ever seen are much sensitive to capacitive loads than their VFA counterparts, a look in the TI reference white papers on CFAs will shed some light as of why. The Zobel and the output inductor helps, of course, but it is fair to say that a CFA requires much more careful design of the output network. While with a conservatively designed VFA you may get along without an output inductor, for a CFA this is very unlikely.
Absolute twaddle, Waly. Regrettably, this is par for the course with you.
Anyway, "papers" are just words from people you never met and don't produce any kind of amplification of audio signals 😀
Loved by people who never build amps but spend their time to argue in forums against other people, who, on their side, build real amplifiers.
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Dont fear, there is no faulty recollection except for the spelling of the name. Indeed the right full name is Prof Willy Sansen and not Sassen.
In time Ill find the particulars I mentioned. He has over 500 papers and 12 or so books, so be patient.
But these papers form the basis of ideas and real world experiments. Maybe you won't like the results but experience is gained.
IMHO it is difficult to design good amps without knowledge.
Hi Bob
See the CFA amp I posted. I made no use of any miller whatsoever but the response is typical 2 pole. See the plots I posted. At the time I mentioned this response but noone even seemed to have noticed. I find 2 pole does includes shunt elements and after studying Sansen work on shunt compensation Im more inclined to say that miller has nothing to do with 2 pole compensation. Keantoken s post is spot on. This 2 pole technique is and has been in use by Yamaha in predomently VFA amps and Accuphase amps (CFAs) for many years.
I posted up a two pole compd CFA a few months back. Simmed at 400w 20 kHz into 8 ohms c 2.7 ppm.
Two pole certainly works with CFA.
Two pole certainly works with CFA.
Papers are interesting when you are looking for explanation about precise behaviors, or want to dig a little further some points, correlating your own experience with other's ones.
You can be sure most of the people publishing their own schematics here have large enough knowledge, refers on their own experience, and are the only ones interesting to read, because they bring something and share .
Not the few ones referring constantly to books or papers instead of their own arguments, living in an abstract world, never publishing anything from their own, for the strange pleasure of a controversy witch looks more like a religious war against CFA. Negative blind believers wanted to show themselves as 'objectivists'. Black smoke.
Read my signature ;-)
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Ahhh! Sander Sassen is the one who designed the ExtremA power amp, there's a thread about it here.
Prof Willy Sansen is the ic design guy, are you sure he's the one who wrote about this compensation stuff?
Jan
See my post to Dave.
Not only Sansen s book but also many of his papers is a requirement in our universties. Sansen doesnt preach shunt compensation for CFA, he explains the characteristics and workings. Then you use what is between your ears and youll realise and understand why shunt is ideal for CFA.
Kindhornman;"..... I would think with all the parasitic parameters that are missing in models that you would see the same thing in electronic simulations vs real world testing of a completed circuit on a board.[/QUOTE said:
The stuff between my ears is telling that shunt compensation is the worst single dominant pole compensation, for VFAs and CFAs as well. Unless you can provide an authoritative reference, this is a fact and you stating ad nauseam otherwise doesn't make it incorrect.
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Wholeheartedly agree with this.
True enough.
Some people may look like they are on a witch hunt. May be they are but they still bring something to the table. If an idea or theory is accurate it should be able to stand up to these challenges. Personally, I find the discussions / arguments in this thread very interesting and valuable. Have to form your own opinion on these things and gain understanding.
🙂
I tend to build very few things.... whether I design/build or buy -- However, I tend to massage them for years afterwards doing circuit mods. I dont do DBLT though on my changes/mods. But I always measure and listen.
I think it is great if a person wants to know all the in's and out's of stabilizing techniques to the Nth degree. BUT as more of a practitioner in this hobby I really dont care and will use the simplest, easiest method... even if it doesn't also get that last drop of distortion ppm. Fortunately with CFA, the BW is so high that i can afford to be lazy about stabilizing it and be not so subtle with the comp and still have little or no affect on audio. Its one of my reasons to use CFA.... However, i understand this here is about SOTA and so the Nth degree and which method to comp the circuit in the best way needs to be covered in some amount of detail.... but just saying I'm not paying very close attention.
THx-RNMarsh
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Some other bias observations..... the THD null is more narrow at 4 Ohm loads than at 8 Ohm load for this EF2 circuit I am massaging. So, I assume that as speaker/load Z goes up and down with freq, the optimum bias level could change enough to affect THD.
Bias level in OPS changes with load Z -- about 15% on this unit.
The signal (music) into a load drives up the heat output and thus the bias transistor reduces the bias voltage, as it should to avoid thermal run-away. So, when the music signal drops, the bias is momentarily low. Its the thermal sink/lag that is an issue, i think.
THx-RNMarsh
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This is indeed what happens.
But if you use the techniques in Self (simming thermal conductance & lag) and Cordell (matching Vbes) you can with care get an EF2 to remain in the low THD slot under dynamic conditions, hot or cold.
I might be incompetent but I don't think this is possible with CFP without ALOT of extra complexity. Anyone done this in 'real life'?
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Anyone got a copy of Self's 6th ed? Please PM me.
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Am I the only one who has noticed that since Waly re-entered the fray, the noise level on this thread has gone through the roof yet again?
Please don't bother replying to 'yus are all idiots & deaf' posts by MikeK lookalikes. It's totally non-productive to man or beast.
Let the moderators deal with his pedantic/semantic ego.
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I understand it exactly the same way, as mentioned in post #5894.
Thermal feedback is relatively slow, and this is a major factor of having the OPS quiescent current drop below the nominal level, after some long high signal heats up the heat-sinks and then disappears.
We have to be fair Esperado, Wally did build very special front-end stage, PCB packed with SMD is perfect to mine humble opinion, apart that he didn't show us any real measurements, I believe it has top notch performance. I think Wally's knowledge is great, we just have to find the right way to communicate positively and we all will benefit from cooperation. 🙂