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The example circuit in the introduction needs a capacitor (or some other high-pass filter) connected between the collector and base of Q3 in order to provide frequency compensation. The circuit as drawn without the aforementioned capacitor has way too much open loop gain in the VA stage especially at high frequencies. This will cause distortion and instability. Relying solely on the Ccb or so called "Miller" capacitance of Q3 to provide adequate local negative feedback is usually considered a poor choice in design practice. — Preceding unsigned comment added by 24.218.178.56 (talk) 01:16, 30 December 2011 (UTC)Reply
EDIT: It would also help if the diagram indicated that both bias diodes and both output transistors must be physically tied to the same spreader bar in order to provide proper thermal Vbe compensation and thus avoid thermal runaway in Q4 and Q5. — Preceding unsigned comment added by 24.218.178.56 (talk) 01:29, 30 December 2011 (UTC)Reply
It also needs a capacitor in series with R7. Without it the output can not settle to mid-rail, which is required for maximum voltage swing and minimum distortion.88.247.150.46 (talk) 18:50, 9 November 2014 (UTC)Reply
I've merged (from a different IP) and then completely rewritten the introduction to class E/F. i hope it clearer now. I've left the remaining description, although in my opinion it is not clear at all, and at time absolutely WRONG (seems to be a transcription from some source by someone who doesn't understand all the details). I recommend removing most of the remaining part in class E/F except my introduction ;)
I didn't remove any existing errors in the old text, because someone is stupidely reverting all my changes when i 'remove' anything... the blantant errors are: class E doesn't output square wave. it is possible to modulate the signal with class E. the text on class F is complete crap. i would remove it completely.
The description of both classes is so poor that is incomprehensible. It misses the basic concepts while concentrating on secondary issues.
In Class-E amplifier the key is that , and resonate at a frequency slightly higher than the carrier and with a well defined damping. The goal is to shape the voltage across the switch in such a way that it drops back to 0 just before the switch is closed. This minimizes losses in the switch as it always operates at zero current, zero voltage or both.
The function of , is simply to filter out anything except the first harmonic of the carrier as usually we don't want to put any rubbish in the load (especially if that's an antenna). Other than that these devices are not a necessary part of the Class-E amplifier.
just provides a DC current (and power) to the circuit and does not contribute to the circuit operation at RF frequencies. Some implementations choose otherwise (i.e. performs the function of ) but the key is operation not the circuit structure.
Adding some voltage and current waveforms would make this section much clearer.
As for Class-F amplifier - again it misses the key idea, which is to block 3rd harmonic so that the voltage waveform across the active device becomes more rectangular, which reduces power losses (the device spends less time in transitions, where both voltage and current values are high).
Also, why not add the schematic of the Class-F amplifier? http://commons.wikimedia.org/wiki/File:Classe_F.svg — Preceding unsigned comment added by 60.37.105.127 (talk) 06:25, 23 September 2011 (UTC)Reply
I think class A amplifier section is wrong. Firstly, a class A amplifier is not another name for an operational amplifier, as the text may suggest. And the diagram is misleading, drawing a BJT connected without any base-emitter current limiter. A BJT with a current generator in the emitter and a load in parallel is the standard way to depict it.
If people agree, I can modify the section.
Romano (talk) 16:06, 11 January 2011 (UTC)Reply
Who first used "Class A" "Class B" etc? —Preceding unsigned comment added by 96.224.72.5 (talk) 21:18, 12 May 2011 (UTC)Reply
The article uses both terms rather randomly and sometimes confusingly. It would clean things up if we chose one or the other. Can we do that? I don't care which really. --Kvng (talk) 01:38, 10 June 2011 (UTC)Reply
The circuit diagrams for A and C are the same. Why do they differ? Is the transistor driven in another manner? Could someone write a sentence to clarify this? -- 178.83.12.182 (talk) 17:51, 20 September 2011 (UTC)Reply
I put a citation needed on the claim that most "quality" op amps have class A output stages. Op-amps, even very good ones, have push-pull output stages. When we use a word like "quality", we create the start of a No True Scotsman argument. What kind of quality? Can we put some kind of number on it? This is someone's opinion that op-amps have to have class A output stages to have good quality. Whoever believes this claim should be easily able to cite part numbers and data sheets to substantiate it, as well as other third-party documentation which shows that those op-amps are of superior quality: measured low noise and distortion figures, and other relevant qualities, like good power-supply rejection ratios, low offset currents and voltages, decent slew rates, etc. 192.139.122.42 (talk) 22:45, 2 October 2012 (UTC)Reply
Class A can be implemented push/pull and still remain class A. This is not mentioned anywhere in the text, and adds to the confusion about op amps. — Preceding unsigned comment added by 66.14.154.3 (talk) 23:04, 25 January 2013 (UTC)Reply
This article was moved from Electronic amplifiertoAmplifier per Talk:Amplifier_figures_of_merit#Amplifier_topic_organization. Olli Niemitalo (talk) 07:54, 31 January 2013 (UTC)Reply
This may be my being to pedantic but the article begins
"An electronic amplifier, amplifier, or (informally) amp is an electronic device that increases the power of a signal."
But I can imagine a circuit where the loaded voltage of a circuit is multiplied but then fed into a high impedance load so it draws very low power (consider attaching an amplifier to an oscilloscope, negligible power out of the amplifier but the voltage has increased.) Is it therefore accurate to say that it is power that is increased? RJFJR (talk) 16:14, 3 May 2014 (UTC)Reply
I entirely agree. Which is why I am changing the opening section of this article, to make this clear. — Preceding unsigned comment added by CatNip48 (talk • contribs) 14:57, 11 May 2023 (UTC)Reply
The term Amplification redirects here. Wikipedia should include somewhere a history of the important concept of amplification. The invention of the amplifying vacuum tube (the Audionortriode) in 1906 created the field of "electronics" (the study of active (amplifying) electrical devices) and made possible all of information technology: long distance telephone lines, practical radio broadcasting, television, talking motion pictures, audio recording, telemetry, computers, networking, etc. I'm prepared to write such a history, but I don't know where it should go. This article is already bloated, and it focuses on a narrower topic: electronic amplifiers, rather than the concept of amplification in general. Gain focuses narrowly on definitions of voltage and power gain. Does anyone have any thoughts about where this history should go? Should there be a new AmplificationorHistory of amplification article? --ChetvornoTALK 07:57, 6 June 2014 (UTC)Reply
I sick and tired of reading about ideal amplifiers . the problem with the explanation of Ideal amplifiers is it is poorly explained all for the sake of high fidelity this is true for books and websites on amplifiers as well as electronic website and webpages online I know there are simpler amplifiers out there that can be easier to explain I once bought a electronics lab kit that had circuits you could build by connecting wires to springs that had electronic components attached to the springs one of the circuits was a basic real world simple amplifier that consisted of one npn transistor one capacitor one resistor a piezoelectric buzzer that double as a microphone a matching transformer and a piezoelectric earpiece although this simple real world amplifier had a lot hissing in it It's still was an amplifier even if it was not a ideal high fidelity one I cannot find this basic simple amplifier or it's explanation on the internet anywhere If human beings continual to give ideal explanations instead of real world explanations human beings will have to go back to living in caves this includes explanations electronics and science richardstephens99@yahoo.com — Preceding unsigned comment added by 2001:558:6044:2:6D51:6199:568C:E550 (talk) 08:30, 30 August 2014 (UTC)Reply
I deleted 'The amplifier is often described as the heart or the nervous system of a microphone or loudspeaker' since
86.29.7.158 (talk) 07:18, 20 April 2015 (UTC)Reply
There should be a section dealing with the history of amplifiers, such as when the amplifier was invented. Blaylockjam10 (talk) 08:04, 28 June 2015 (UTC)Reply
I'm going to (slowly) start to clean this article up, feel free to help if you want to. The things I think need work:
What does anyone think? I'm going to go ahead and start to implement some of these changes, feel free to either help or stop me! — crh 23 (Talk) 19:20, 18 June 2016 (UTC)Reply
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Today user:Chetvorno reverterd my edit. They provided as arguments:
Incomprehensible for general readers (what is the "value" of a "signal"), has factual errors (all amps increase the power of a signal), is not an adequate summary of article
I would like to discuss this here. First, the statement "all amps increase the power of the signal" seems incorrect to me. I will explain my reasoning with an example. Say I have a current source as input to a system (eg, photodiode). I would like to turn this into a voltage. To do such, I use a shunt resistor and feed the voltage over this resistor into a voltage amplifier with voltage gain of 100. For the sake of the example, let's say that I have a 1mA input current. I use a 5ohm shunt resistor. I find a voltage drop of 5mV. This would mean that the input signal is providing me with 1ma*5mV=5uW of power. My voltage amplifier has an output of Av*Vin=100*5mV=0.5V . If this is then fed into a second voltage amplifier stage, with a very high input resistance (as you desire with a voltage signal) of say 10Mohm (quite a reasonable number for say a MOSFET gate at a not-to-high frequency). This means we get a current of 0.5V/10Mohm=50nA. The power would hence be 50nA*0.5V=25nW. In other words, even though my amplifier has a voltage gain of 100, it has a negative power gain - we go from 5uW to 25nW of power. Unless you can disprove my calculations, I thus don't see why "not all amplifiers provide power gain" is a factual error.
As for your other arguments: I can agree with you on "value" of a "signal" being somewhat abstract, but this can be improved then by adding examples. The fact of the matter is that amplification is the increase of a value of a signal (and not neccesaraly power, we like to keep that as low as possible for as long as possible because power means heat), in the case of a voltage amplfifier it is the voltage of the input signal... I feel like the current introduction implies first that only voltage, current, transconductance and transimpedance amplifiers exist. At the same time, it also seems to suggest we only ever care about power, which is not correct (see my example above). Even if we come to the conclusion of my changed introduction being bad, I feel it still requires a rewrite. I would thus like to open discussion about this topic, to avoid getting into a revert war. Regards, TheUnnamedNewbie (talk) 10:05, 2 February 2017 (UTC)Reply
Class B has two active gain devices. One providing gain for for positive excursions of the signal from zero. The other providing gain for negative excursions. Each device theoretically operates for 180 degrees of the signal and is off for the other 180 degrees, effectively a rectifier for the signal. In practice, near zero signal level, both gain devices are off, which causes the output signal to be distorted.
The article is describing a class C amplifier, which has only one gain device and amplifies for 1/2 the period. This is probably because the cited source is a poor reference.
For example, an NPN transistor does not turn on and begin to amplify until the base voltage reaches the threshold voltage. Typically the threshold voltage is around .65 volts. Likewise, a PNP transistor turns on at -.65 volts. Thus when the input voltage is between -1 and 1 volts, significant distortion occurs as both devices are off. To correct the problem of the B amplifier, the AB amplifier was developed. The transistors are biased so that both are in their active zone when the input signal is near zero. --74.46.101.158 (talk) 16:33, 21 April 2017 (UTC)Reply
This is a deep subject. "Electronics Engineers' Handbook" has a 146 page chapter on amplifiers and oscillators, and *that* is still an overview (ok, so maybe 40 of those pages are about oscillators). Any specific details must be spun out to other articles, and this article should be only a 20,000 foot overview of the field. Even so, there's so much that hasn't been touched on here - stability, load lines, economics! Luckily a lot of the details are available already in other articles, we don't have to go on about tube sound here, for example, just point at it. --Wtshymanski (talk) 16:53, 7 May 2017 (UTC)Reply
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The 3rd paragraph of the introduction was recently changed from:
to:
The reference to "electro-mechanical signal repeaters" is to speakers driving carbon microphones to make a crude electroacoustic amplifier, which had very limited use as telephone line repeaters during the first two decades of the 20th century.
While they are quite properly described in the History section, I think mentioning them in the introduction gives WP:UNDUE WEIGHT to this trivial dead-end technology. Carbon repeaters were truly horrible amplifiers, being insensitive, having sharp resonance peaks, DC offset problems, and introducing noise (the "carbon roar"). They were only used in a limited way in telephone lines, and had almost no usage in other applications of amplification. There are many more notable points about amplifiers in the article which should be mentioned in the introduction before mentioning this device. --ChetvornoTALK 21:50, 3 June 2017 (UTC)Reply
The result of the move request was: not moved (non-admin closure) ~SS49~ {talk} 07:21, 16 May 2020 (UTC)Reply
Amplifier → Electronic amplifier – Some people make the mistake of thinking that Electrical Amplifiers are the only type of amplifier, but please see Amplifier (disambiguation)#Other amplifier types - mainly Magnetic amplifier, Mechanical amplifier, Optical amplifier, Pneumatic amplifier 83.137.6.117 (talk) 10:41, 8 May 2020 (UTC)Reply
The result of the move request was: not moved. (closed by non-admin page mover) – MaterialWorks 20:11, 11 September 2023 (UTC)Reply
Amplifier → Electronic amplifier – 1) The article opens with the hatnote: This article is about electronic amplifiers... 2) Then begins with an immediate disambiguation: An amplifier, electronic amplifier, ... 3) It is the main article of Category:Electronic amplifiers4) The category Category:Amplifiers is subdivided into the two subcats Category:Electronic amplifiers and Category:Mechanical amplifiers, the latter of which has its own main article. Summary: All of the above indicates that the best title for this article is "Electronic amplifier" Gjs238 (talk) 16:11, 4 September 2023 (UTC)Reply
The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.