Waly wrote "This deserves at least a separate book, in fact only the "feedback in switching systems" topic can, and already does, fill a full shelf."
The subject falls firmly and squarely within the realm of standard control theory. We ship about 350 million switching controllers a year and have the comp well nailed.
The subject falls firmly and squarely within the realm of standard control theory. We ship about 350 million switching controllers a year and have the comp well nailed.
All you seem to be able to do is criticize. That is not productive. If you knew much about class D I would be more inclined to take seriously your description of my class D chapters as cr*p.
I asked you to come up with specifics and you provided nothing. What a shame for a youg man who is obviously well-educated, yet completely inept when it comes to constructive discourse.
I will try to address your general criticisms in the second edition, as I genuinely want to improve the book. However, there is no way I will drop the class D section. It will improve and get larger.
In the meantime I have two suggestions for you:
1. Try writing a book that is targeted to a wide audience on a technical topic.
2. Try reading a book on improving how you act more professionally in communications with others.
Cheers,
Bob
Bob,
The class D chapter is one I haven't read. The question is why would some one buy your book? Is it the analogue side of things or the digital? 90% of the book is concerned with analogue and 10% digital. Why would someone buy it for the digital side of things alone?
The trouble is a lot of the class D IC's have detailed datasheets and application notes already associated with them. You would indeed need a whole book dedicated to class D to be able to add any more detail to these datasheets that are already available.
My vote would go with scrapping the class D section if it meant adding / expanding on other ideas associated with the analogue theory.
If it had a whole section on CFB that would be enough for me to get the 2nd edition.
The class D chapter is one I haven't read. The question is why would some one buy your book? Is it the analogue side of things or the digital? 90% of the book is concerned with analogue and 10% digital. Why would someone buy it for the digital side of things alone?
The trouble is a lot of the class D IC's have detailed datasheets and application notes already associated with them. You would indeed need a whole book dedicated to class D to be able to add any more detail to these datasheets that are already available.
My vote would go with scrapping the class D section if it meant adding / expanding on other ideas associated with the analogue theory.
If it had a whole section on CFB that would be enough for me to get the 2nd edition.
Bob, i generally do not buy books about electonic, as i prefer to look at schematics and experiment by myself. But what i have to say about the parts of yours i've read here or here is:
Yes, you do not provide always detailed calculations. But you provide what is useful, and what, by habit we only memorize ourself. Like this 33% to heat your room
And it is highly recommended that every body make they own calculation and measurements in order to understand and feel more deeply once they have understood the general operation of a circuit .
More than this, your point of view of the way the electrons across this crap that an electronic circuit is are often full of light with accurate focus point.
Along years, we all got 'feelings' about the way behave (and sound) a particular arrangement of active devices (diamond buffers, cascodes, current sources, CFAs etc.).
Sometimes, your words change in a positive and more accurate way those feelings. You know, like some blues tune can help-you, sometimes, to feel differently 'the blues'.
It is a hard work to write the kind of book you write, between school books, and audio book, for tired engineers as well as pretentious students.
I am curious about your future inputs on class D and CFA, as i'm sure you will experiment ... and smell
Thank for all the things you share, and thank for the pleasure i had reading your web site, making lot of us to feel ... less lonely ... in this endless quest of music and this stupid electronic near blind jiggering.
You are a nice and lovely gentleman, keep on truckin', please.
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If i had a book to write about electronic, i would talk about
- Components and their evils [distortion in resistances, due to magnetic or thermal effects depending on their technologies, condensers (mechanical resonances, included inductances eq impedance resonances), transistors and various fets and mosfets technologies (thermal effects, parasitic capacitances and their variation with levels etc.)]
- Where and why to take care of those evils (like resistance distortion in feedback path, how to parallel various capacitance to minimize impedance )
- How to set a correct attitude between voodoo and pure mathematical way to think. (like cables) and the importance of listening, measuring and get a good understanding of the correlation between those.
- Description of the distortions and their subjective importance on our listening experience...
- Various Feedback (local and global) advantages and evils.
And, of course, the description and analyses of most of the know amplification arrangements and their parts around: power supplies, various class of amplification etc. and where to look-at to take the best of it.
Better a good way to think than extended uncorrelated samples of knowledges.
- Components and their evils [distortion in resistances, due to magnetic or thermal effects depending on their technologies, condensers (mechanical resonances, included inductances eq impedance resonances), transistors and various fets and mosfets technologies (thermal effects, parasitic capacitances and their variation with levels etc.)]
- Where and why to take care of those evils (like resistance distortion in feedback path, how to parallel various capacitance to minimize impedance )
- How to set a correct attitude between voodoo and pure mathematical way to think. (like cables) and the importance of listening, measuring and get a good understanding of the correlation between those.
- Description of the distortions and their subjective importance on our listening experience...
- Various Feedback (local and global) advantages and evils.
And, of course, the description and analyses of most of the know amplification arrangements and their parts around: power supplies, various class of amplification etc. and where to look-at to take the best of it.
Better a good way to think than extended uncorrelated samples of knowledges.
The strangest experience I had of this was a MM preamp I knocked together out of junk . Good junk . 10 nF 3 cents Mylar capacitors measure to 0.5% ( green 100 V ) . TL074 . The design was passive ( 75 uS ) + active . The 318 + 3180 correct to 0.2 dB . Identical between channels . Dead bug . The cartridge Linn K18 ( LP12 EKOS ) . I listened to it for 10 minutes and gave up . Some months later it was still running . My friend discovered it and announced how wonderful it sounded . Produced a Schroeder pick up arm and Tracy Chapman was in the room . Dammed if I know why it was like that . TL074 was what I had rather than a choice . Placebo or the anti Placebo ?
The silly pre amp was taken for a tour of Europe . It got a MC33079 when it did . I did try a fancy LT 11??? 0.9 nV op amps in it's place . Not sure it worked better . Brighter .
The silly pre amp was taken for a tour of Europe . It got a MC33079 when it did . I did try a fancy LT 11??? 0.9 nV op amps in it's place . Not sure it worked better . Brighter .
Of course class D is analog technology. It concerns itself with voltage, current, time - all analog quantities.
Digital concerns itself with quantities coded in binary numbers.
Yes I do know what you mean, but as soon as you realise it is all analog, you can learn a lot from Bob's book in the non-class-D chapters that will help you to understand class D as well. Control theory is control theory.
But I would also like to see the class D section expanded. As Bob notes, it is a fast moving area and I am sure he will pay attention to it in his next edition!
jan
This -->
... a follow-on to my previous comments would be:
The Extra bandwidth in modern C-Mode opa is acheived because the op-amp is being used with input and output nodes held at virtual ground.
For low distortion -> Inside the opamp there will be no large voltage swings at high impedance nodes to limit the speed of operation.... and the large volatge swings contibute to causing increased distortion.
THx-RNMarsh
I use to make distinction between what i call pure analog (levels treated as levels), vs other methods to transmit an analog signal where an other property (duration of a square pulse clock or frequency in case of FM) is modulated in a proportional analog way (infinite numbers).
I agree with the mcd99uk's distinction, as PWM share with digital delta sigma (digital) topology, the oscillator, the comparator, the use of feedback and the output filter to reject the clock frequency.
I probably deserved this, for trying to be honest about (and following your request for suggestions).
Do whatever you like, I will certainly not going to purchase the next edition for the 50 extra pages of Class D handwaving. And do yourself a favour and stop patronizing people.
Clocks are analog circuits. If you would try to design a clock circuit that would be immediately clear!
Same for comparators. High speed analog circuits!
jan
Jan,
Class-D always seems to bring in the analog vs digital domain conversation. When we add in a section that takes us from analog and converts to digital and then back to analog AD to DA then we can discuss digital amplification. But I also understand the thinking of PWM and how it seems to be almost digital in nature. A very sticky wicket as the English would say.
Class-D always seems to bring in the analog vs digital domain conversation. When we add in a section that takes us from analog and converts to digital and then back to analog AD to DA then we can discuss digital amplification. But I also understand the thinking of PWM and how it seems to be almost digital in nature. A very sticky wicket as the English would say.
Yes there are amplifiers that accept digital signals or internally do a A/D and at that point revert to digital processing.
Don't see why it is a sticky wicket?
The problem is that when you use the wrong term 'digital' for class D, you forego the fact that it is useless to try to design a class D amp unless you are very, very good in analog design.
One of the nice things with A/D and D/A designs is that it taxes the designers abilities in both analog and digital design, which makes it pretty hard to design a first rate DAC, for instance.
One issue that still makes it difficult to design first rate class D amps is that there are very few designers in audio that are experienced in high speed analog design. Feedback and control in class D is also something that goes a bit beyond the ubiqutous (sp?) miller comp cap
And if you look at the issues with grounding and power supply routing in class D, that's an analog issue if there ever was one, and very critical.
Edit: I think what I want to say is that when you are very good in analog design you can probably design a passable class D amp on first try. If you are a digital systems designer, no way you will be able to design a good class D amp!
jan
Don't see why it is a sticky wicket?
The problem is that when you use the wrong term 'digital' for class D, you forego the fact that it is useless to try to design a class D amp unless you are very, very good in analog design.
One of the nice things with A/D and D/A designs is that it taxes the designers abilities in both analog and digital design, which makes it pretty hard to design a first rate DAC, for instance.
One issue that still makes it difficult to design first rate class D amps is that there are very few designers in audio that are experienced in high speed analog design. Feedback and control in class D is also something that goes a bit beyond the ubiqutous (sp?) miller comp cap
And if you look at the issues with grounding and power supply routing in class D, that's an analog issue if there ever was one, and very critical.
Edit: I think what I want to say is that when you are very good in analog design you can probably design a passable class D amp on first try. If you are a digital systems designer, no way you will be able to design a good class D amp!
jan
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Well, in a way, yes, a mechanical resonator (quartz) and an amplifier... let me think about... analog to what ?
Same question for comparators... Are they analog ? Not in my catalogs... only two states, finit numbers... let me think about...
I think we can describe as digital a signal defined by a finite numbers of well defined steps.
If you accept this definition, as each pwm pulse duration is infinitively variable in proportion of the level, we can describe-it as analog.
About well defined steps, unfortunately, each ripple of the psu in the audio range will be transmitted (after reduction by the analog feedback) in the speakers... Analog here too.
For our safety, we have to sign a non disclosure agreement about the feelings you describe: "it seems to be almost digital in nature".
And a good one with little help from a digital designer for precise clocks and comparators ?
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And a good one with little help from a digital designer for precise clocks and comparators ?
I can't fathom why you think clocks and comparators are digital??
Bandwidth, rise time, positive feedback in a comparator, what's digital about that?
An oscillator is an analog circuit with positive feedback. You can replace the frequency determining element with a xtal, but it is still an analog amplifier circuit.
jan
Well you ARE creative, I give you that. You have just described a sampled system. It becomes only digital if you code those step values in a digital byte or word and operate on that.
Like the output of an ADC - the input is analog, and the output is a digitally encoded value.
There are digital amps that take such a digital encoded value as input and those could be called digital amps.
Class D accepts analog in, gives analog out, and at no time is the internal processing anything but analog.
jan
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I can't argue with what Jan has said. I think the point was made above about class d being PWM. This as a topology is a world away from the IPS/VAS/TIS/OPS topologies of a class A/AB/B. And this is the distinction I would like to make.
I can see where there is some crossover between the two technologies, however, this could be covered in separate sections and not a pure class D section. eg. grounding / ground planes (which I will not entertain at my level of ability) is just part of good design.
I can see where there is some crossover between the two technologies, however, this could be covered in separate sections and not a pure class D section. eg. grounding / ground planes (which I will not entertain at my level of ability) is just part of good design.
Did i said that ? Or did i said "let me think about" ?
Apologize for the "s" of numbers.
And look at your "word" or at my "finite numbers".
I'm too lazy to send you a sample of music written by hand with arabians numbers.
What you call digital in English is called "Numeric" in my language (and your ?).
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I stand corrected. Finally I find someone who is willing to think and I messed it up!
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