Talk:Amplifier

Example Circuit

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)

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)

Class E/F

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.

Your IP changed. See User talk:217.132.20.249 for your edits on electronic amplifiers. You should just get an account. — Omegatron 22:25, 31 March 2006 (UTC)

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 $L$, $C$ and $R_{L}$ 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 $L_{0}$, $C_{0}$ 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.

$L_{1}$ 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. $L_{1}$ performs the function of $L$) 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)

Class A amplifier problems

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)

I agree that the mention of op-amps is unhelpful, so just remove it. There is an "Operational amplifiers (op-amps)" section, and I do not think it needs any mention of "class". The diagram is problematic: yes, it's wrong, but exactly what alternative would be better? The point of the diagram is to give a very vague overview, while showing accurate i/o waveforms. I cannot think of any simple improvement that would not reduce its accessibility for general readers. There perhaps could be some mention like "bias circuit not shown", but the same applies to some extent in all the "class" diagrams. Johnuniq (talk) 00:48, 12 January 2011 (UTC)

Etymology of "Class A"

Who first used "Class A" "Class B" etc? —Preceding unsigned comment added by 96.224.72.5 (talk) 21:18, 12 May 2011 (UTC)

Valve vs. vacuum tube

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)

A C distinction

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)

The tet does explain the difference. The waveforms would be more illustrative if they were properly referenced to 0 volts. It's hard to see how teh Class C amp can have an output that swings negative with respect to ground... --Wtshymanski (talk) 18:51, 20 September 2011 (UTC)

Added citation-needed for op-amp claim

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)

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)

Article moved from Electronic amplifier

This article was moved from Electronic amplifier to Amplifier per Talk:Amplifier_figures_of_merit#Amplifier_topic_organization. Olli Niemitalo (talk) 07:54, 31 January 2013 (UTC)

This article is still sorting on "electronic amplifier". Is that what people want? Not sure what the best decision is here. Jason Quinn (talk) 04:48, 30 March 2013 (UTC)

amp always increase power?

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)

Yeah, most definitions 1, 2, 3, 4, 5 don't seem to limit "amplifier" to devices that increase the power of a signal, but also include devices with voltage or current gain. One that I like says "a device that uses an external power source to increase the strength or magnitude (power, voltage or current) of an electrical signal". --Chetvorno^TALK 20:19, 7 June 2014 (UTC)

History of amplification

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 Audion or triode) 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 Amplification or History of amplification article? --Chetvorno^TALK 07:57, 6 June 2014 (UTC)

I think your proposed information should go into amplification which would therefore be changed from a redirect into an article. Binksternet (talk) 14:30, 6 June 2014 (UTC)

Thanks, I think that's probably the best idea. Another possibility that occurred to me is to include it in the Electronics article, since the invention of amplifying devices was pretty much synonymous with the birth of electronics. --Chetvorno^TALK 20:27, 7 June 2014 (UTC)

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)