Talk:Class-D amplifier

message: The easiest way to explain how Class D works is to have an animated gif of a normal wave form next to a square wave with pulse modulation of the same sound.   — Preceding unsigned comment added by 24.246.52.178 (talk) 20:10, 14 April 2023 (UTC)

message: Not to nitpick, but the low-pass filter show in the block diagram figures shows the symbol of an inductor where a resistor should be used instead. Can this be fixed by whoever has the original .svg file?
Saket (talk) 17:34, 6 October 2009 (UTC)
thread_title:  Block Diagram Needs Updating 

message: Suggest that this article be merged with Electronic amplifier#Class_D. Wasn't aware that this has been covered elsewhere at the time of creation. Rohitbd 12:56, 5 August 2005 (UTC)
replies: text: See Talk:Electronic_amplifier - Rohitbd 09:10, August 8, 2005 (UTC)
Another application worth mentioning for the Class D amplifier, especially in context to handling digital signals, are home-theatre receivers or home theatre in box systems that are based on this technology. Typically, they would use analogue-digital circuitry (for analogue inputs including the AM/FM tuner), accept digital inputs directly and do the processing or decoding in the digital domain before putting the signal out to Class-D power-amplifier circuits (typically 5 or 6 in the units that are affordable for most people). This is usually to permit the design of compact affordable equipment.
SimonMackay (talk) 14:14, 11 February 2008 (UTC)
thread_title:  Misc 

message: The article discusses their advantages but not their disadvantages.  How come Class D amps aren't everywhere?  — ciphergoth 08:43, 24 October 2007 (UTC)
replies: text: It seems to me, that with current technology, the extra work to design a good class-D amplifier is only worthwhile at higher power levels. Gah4 (talk) 01:07, 2 May 2019 (UTC)
thread_title:  Disadvantages of Class D amplifiers 

message: (16:06, 22 October 2007):"Standard Class AB high-wattage power amplifiers are very heavy due to their bulky transformers and heat sinks. Class D amplifiers are lighter in weight and smaller than standard Class AB amplifiers, because they are more efficient. Class-D amplifiers use MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) rather than BJT transistors and they generate a triangular pulse waveform which is filtered at the output stage with a low pass filter to remove the high frequencies."
In these two sentences I have tree things to disagree with:
* The major distinguishing property of the switching is some lossless amplification. The elimination of weight of heat sink is a secondary, side, collateral, attribute of any non-dissipating device. (This is mainly an assent issue, but it is important to understand the principle rather than effects and applications, I believe)
*I'm sure, nobody uses the transformers to amplify the power.
*The transistors generate RECTANGULAR waveform rather triangular. The D-amplifier article authors even do not understand that the switches can generate nothing but the rectangular! The energy saving principle misunderstanding explains their misroute focusing on the wight. --Javalenok (talk) 17:01, 5 January 2008
:I have corrected the edit today. --Javalenok (talk) 11:31, 6 March 2008 (UTC)
replies: text: Your modern amp is a Class T though, not merely a Class D. We have to be careful with these articles as to what goes where. I still favour keeping them separate, and expanding each accordingly, even if that involves duplicating content between both. Clarity for readers is an issue, communicating the whole story is an issue, pasting some content is not an issue. Andy Dingley (talk) 13:59, 4 September 2017 (UTC)
thread_title:  Some absolute crap in the abstract (introduction) 

message: I really think that this article should be split such that "Switching Amplifier" would be an overview article with an explanation of switching and only brief descriptions of the different classes.  Details belong in separate articles that get referenced hierarchically.  Much of this article would end up as "Class D Amplifier" or somesuch, and "Class T Amplifier" would either become a section of that or would get hierarchically referenced below "Class D Amplifier".  My preference is the latter.  Esobocinski (talk) 19:59, 27 March 2008 (UTC)
replies: text: Yes, that's the way to go - an overview article that makes it clear what they have in common that makes them a class or category, and some discussion of key differences (how they use feedback?); with separate articles (and categories) for specific topics and implementations.  There are going to be more and more implementations of switching amplifiers, both because (1) the technology has now reached a level where full frequency range (and not just subwoofer) applications are used in the mass market and for audiophiles; and because (2) the low energy consumption / "green" aspect is becoming more valued.  141.154.19.152 (talk) 01:31, 5 June 2008 (UTC)
thread_title:  Make "Switching Amplifier" an overview and reference separate articles about classes 

message: Is this paragraph accurate?
"The term "Class-D" is sometimes misunderstood as meaning a "digital" amplifier. The quantization of the output signal at the power stage can be controlled by either an analog signal or a digital signal. Only in the latter case would an amplifier be using fully digital amplification."
Seems to me this is a confusing use of the term "digital."  Aren't all amps essentially analog devices at their output stage?  I understand that the circuit can be driven by a quantized "digital" signal.  I don't see how this makes the amp "fully digital."  A class A/B being driven by a quantized signal wouldn't be considered digital just because it was being fed a quantized signal.
75.71.201.190 (talk) 05:07, 15 August 2008 (UTC)
replies: text: I'm not sure what's confusing about that sentence. I think it's point is that even though the SMPS switches amongst a discrete set of values, it should not be said to have a "digital" output. A traditional SMPS amplifier has an output that assumes two states (e.g., on/off, high/low). These two values certainly come from a discrete set, but the switching times can occur at any time. That is, the switching times are not necessarily quantized in any particular way. So the switching times are themselves an analog signal. When an SMPS device is driven by a PWM signal (as opposed to, say, sliding mode methods), if the duty cycle can take any value from the continuum [0,100]%, then the output is analog. However, if the PWM signal is generated by a digital source (e.g., a counter that turns off after a certain number of counts), then the duty cycle will be quantized. —TedPavlic (talk) 20:17, 26 June 2009 (UTC)
thread_title:  "Fully" Digital 

message: This is a follow-up to the Talk section immediately preceding. Mr Pavlic is basically correct, and everything else is, to a greater or lesser degree, wrong. The article needs to be edited to bring it in line with what Mr Pavlic says.
I find it amazing that the overwhelming majority of engineers and technicians do not understand the difference between analog and digital. Simply stated, a class D amplifier can be digital or analog, depending on whether the samples "driving" the output are quantized or vary continuously. Yet when you point out this obvious and easily understood distinction, most people become violently offended, generating gallons of technical bilge of what "digital" really is, or how a signal can be both digital and analog at the same time. Mr Pavlic is that extremely rare exception; he understands. WilliamSommerwerck (talk) 22:03, 13 June 2012 (UTC)
thread_title: inaccurate "Terminology" section

message: I have an Electro Voice powered PA sub, on which back (where the built-in amp is) it says Class-D Digital Amplifier.  —Preceding unsigned comment added by 77.35.41.134 (talk) 09:58, 28 February 2009 (UTC)
thread_title:  d-amplifier term 

message: Question - for the non-feedback type wouldn't voltage drift be a problem - no two components are exactly identical. Maybe in practice this is inconsequential? since typical loads are not purely capacitive.
Is this an acknowledged factor - if so could drift be mentioned.77.86.67.245 (talk) 21:50, 23 April 2009 (UTC)
replies: text: Of all performance issues that non-feedback amplifiers suffer, DC offset and associated thermal drift is the least serious one. A power stage would contribute a DC error if the FETs turn on/off at unequal times, but since non-feedback designs invariably use very fast switching you're unlikely to find more than a few tens of mV at the output. This is neither unusually large nor problematic. Classedhaie (talk) 06:45, 19 May 2010 (UTC)
thread_title: Drift

message: "Digital" amplification is something I've been hearing a LOT about lately, and much if not all of it is not related at all to traditional Class D pulse wave modulation concepts in all of its analog glory. After reading about NAD's new M2 Direct Digital Amplifier, it seems to me that the redirect from 'digital amplification' to this Class D article is now unwarranted (which is how I arrived here in the first place), because there IS newer technology that is derived from silicon-based "amplification" that is claimed to be "true digital" and that the Class D connection is not the case anymore--at least not in the traditional sense--regardless of any misnomers or mix-ups made in the past with the "genotype". 
http://nadelectronics.com/img/datasheets/M2-white-paper-EU-Web.pdf   Monoblocks (talk) 06:39, 19 September 2009 (UTC)
replies: text: The NAD amp (Zetex) is actually remarkably analogue. First, a "clean" small-signal PWM signal is made using a fast logic gate, a low-jitter clock and a very stable reference supply. The output voltage of the power stage is compared (using an analogue difference amp) with the "clean PWM reference" and the error integrated using an analogue integrator. The integrated error is then digitized so the controller chip can correct the PWM control of the output stage. This is effectively Karsten Nielsen's PEDEC circuit, except that there's an extra AD conversion in the "local loop". Since the output voltage is compared to the "clean PWM reference" and any differences reduced by feedback, the reference is actually the signal that is getting amplified. You can easily show this by injecting an analogue audio signal into the error amp along with the reference while no digital input is present. You will get a high-quality amplified version of the analogue signal at the speaker terminals. A better way of describing the Zetex design is an analogue PWM amp with additional digital processing inside the control loop, and with a ripple precompensator at the input. In absolute terms, the performance of the NAD amp is good (and it sounds the part), but the control structure is more complicated and contains more digital processing than needed to get to this level of performance. But however you slice it, an enjoyable listen. Classedhaie (talk) 06:57, 19 May 2010 (UTC)
thread_title: Class D vs Digital

message: When were these things invented? When did they become practical and popular? Dbagnall (talk) 10:20, 10 February 2012 (UTC)
replies: text: Indeed, some history would be nice.  There is absolutely none at all in the article! Who developed the first one, what products they were first used in and why, when and why they made it to various levels of the audio markets... Huw Powell (talk) 13:44, 20 December 2014 (UTC)
thread_title:  A bit of history would be nice 

message: Why does "Transistor Amplifier" redirect to "Class-D amplifier"?  There are other classes too.  — Preceding unsigned comment added by 220.244.96.30 (talk) 08:28, 17 March 2012 (UTC)
replies: text: Hm you're right, this redirect is not helpful. Actually I'm not sure if it's a good idea to have an entry called "transistor amplifier" at all. The only place the term is ever used is in audiophile circles to make the contrast with "valve amplifier". Ontologically this is not an effective way of understanding the world. Imagine wikipedia having separate entries for control theory depending on whether we're talking mechanics, hydraulics or electronics, let alone using valves or transistors. I'd vote for the removal of the "transistor amplifier" redirect altogether, but I'm not sure how to go about this.Classedhaie (talk) 13:46, 8 May 2012 (UTC)
replies: text:  Redirect it to valve amplifier, and have a section in there describing the (alleged!) "transistor sound". Andy Dingley (talk) 13:56, 8 May 2012 (UTC)
thread_title:  Redirected from "Transistor Amplifier" 

message: User 96.224.66.232 had added this inside the section intended for terminology: "A purely digital amplifier with no feedback would have zero power supply rejection.[1] Real class D amplifiers use analog input stages as part of the rejection circuit, while amplifiers with digital inputs must emulate this feedback loop in software. True digital Class D amplifiers are rare."
This relates to technical execution, not so much terminology. Also, the point is already made in clearer terms under the error control section. A term like "true digital amplifier" is unclear, especially considering the fact that anything able to drive a speaker must be analogue, however implemented. For future edits relating to the species "true digital amplifier", consider using the term "open-loop digitally controlled amplifier" instead. The only new point the bit I removed makes that wasn't in the article is that an open loop controller can be improved by measuring the supply voltage in order to cancel supply ripple. So I'll add that to error control. Classedhaie (talk) 13:25, 8 May 2012 (UTC)
thread_title:  Removed duplicate explanation 

message: The section about supply bus pumping conflates a number of things. On half bridge amps, excess power is always drawn from one rail (depending on the sign of the output current) and dumped into the other. This will happen equally with purely resistive loads. Full bridge amps return energy whenever the sign of the output voltage and output current are opposite, which means that it only happens with reactive loads. It might improve clarity to fix this item.Classedhaie (talk) 07:09, 12 June 2012 (UTC)
thread_title:  Bus pumping 

message: There is really no discussion of distortion except to mention it "in passing" in a few places. How can an article on an amplifier class not talk in detail about the kinds and effects of distortion? Intermodulation, total harmonic etc. Are there inherient limits or types with this class? How are the design challenges met? What can the user expect from this topology? ...  — Preceding unsigned comment added by 97.86.249.149 (talk) 13:03, 24 June 2012 (UTC)
replies: text:  The article discusses distortion in greater detail than you'd think at first perusal. It mentions the dominant error sources (dead time, power supply ripple, the LC filter) and the main method of combating it (adding negative feedback, for instance a PID controller, around the amp). Harmonic distortion and IMD are not 2 different kinds of distortions but two different manifestations of the same nonlinearity. What is worth adding at some point though is a section on distortion arising in the modulator, and that dead time distortion manifests itself as a non-linear output resistance in series with an idealised version of the amp. Spelling out the gory bits would become a bit redundant I guess. The article is more in need of a structure than of further details.Classedhaie (talk) 10:43, 3 August 2012 (UTC)
thread_title:  Distortion 

message: Class-D amplifier is an electronic circuit that has the ability of gain, but it's not the analogue-acting amplifier, and this is why so simple linking to amplifier is risky. This is switching amplifier or pulsating amplifier – very close to the principle of switched mode power supply. I suggest to fix the definition. --Robsuper (talk) 12:36, 11 April 2013 (UTC)
replies: text: Yes, Class D amplifiers exhibit analogue gain.  Looking at their internals, they use PWM. However, from the outside, they also make use of a low-pass filter. The result of this (c.f. Fourier, I hope I don't have to spell this out) is that their overall behaviour is indistinguisable from an analogue amplifier. Andy Dingley (talk) 13:58, 11 April 2013 (UTC)
replies: text:  If you treat such amplifier as a "black box" then yes: an analog signal at the input and at the output. However way for a particular purpose, and I am thinking of booster effect, is quite different - variable filled short pulses. The amplifier can not give energy without using properly selected low-pass filter attached between its output and the receiver (load). In applications the problem is the high level of noise from output transistors acting here as controlled switches - this disadvantage is the distinguishing feature of this type of signal amplification method. Thank you for kind response. --Robsuper (talk) 11:23, 16 April 2013 (UTC)

text: I think the second paragraph makes abundantly clear that "amplifier" need not imply "linear gain block". Class D audio amplifiers are particularly curious in that respect in that they behave (as much as their designer can make them) like a linear gain block even though the actual power stage is decidedly nonlinear. That does not detract from the fact that said power stage is still an amplifier for the relevant intents and purposes. It turns a small PWM signal into a big one. That's what it's asked to do and it does it well. The fact that on its own it'd be hopeless when called upon to amplify a sinewave is irrelevant. Its task is to amplify PWM, not sinewaves. That's the task of the overall circuit that beyond the switching stage includes modulation, error control and output filtering. Engineers define amplifiers operationally, not mathematically or abstractly. If a given contraption makes the signal bigger in the context that I'm using it in and with sufficient precision that I can use it, it's an amplifier.Classedhaie (talk) 09:16, 25 April 2013 (UTC)
thread_title:  The definition 

message: I just removed the addition "in digital amplifiers" from "The same errors will only lead to incorrect results in digital amplifiers when they become so large". Those three words were out of context. The sentence refers to transmitting digital signals (e.g. computer data) and recovering them exactly from their physical representation. No audio in sight.Classedhaie (talk) 09:20, 25 April 2013 (UTC)
thread_title:  Clarification 

message: Hello fellow Wikipedians,
I have just modified one external link on Class-D amplifier. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
*Added archive https://web.archive.org/web/20110724163006/http://www.piak.nl/pdf/REF24.pdf to http://www.piak.nl/pdf/REF24.pdf
When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.
Cheers.—InternetArchiveBot (Report bug) 23:52, 8 August 2017 (UTC)
thread_title:  External links modified 

message: The article mentions the difference between class D amplifiers and switch-mode power supplies.  I believe I have known amplifiers with non switch mode outputs that adjust the SMPS to keep power dissipation down. At lower power levels, the power supply generates a lower output voltage, and appropriate negative feedback allows appropriate output.  This would mix up the meaning difference between class-D and other classes. (I don't remember which amplifiers I thought I knew that did this, though.) Gah4 (talk) 01:14, 2 May 2019 (UTC)
thread_title:  SMPS and amplifiers?