Talk:Voltage source

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Added some voltage source circuits. Page may need wikifying. -- Rohitbd 9 July 2005 16:32 (UTC)

1 Voltage Source
- 1.1 Class AB Amplifier biassing
2 Infinite power during short circuit?
3 Potential divider "source"??
- 3.1 Potential divider source
4 "Battery" or "cell"?
5 Title of Page
6 Mains Electricity
7 Neutrality
8 Sources used in electronic circuitry
9 Capacitor as voltage source
10 Introductory para
11 Two voltage sources connected in parallel
12 Combinations and simplifications
13 New structure

[edit] Voltage Source

Does any one want to explain what this para is about before I alter it mercilessly or delete it? Even the grammar does not make sense#!!

In class-AB amplifier applications, a shortcoming of this circuit causes it to act as a "bias servo". Since VBE decreases with increasing temperature, thereby reducing the VBE multiplier's output voltage, this circuit when used to bias the output stage of a class-AB amplifier also doubles up as a compensator for increase in the temperature of the output devices - increase in temperature causes the bias voltage to decrease thereby causing the output devices to run at a lower current and in turn produce less heat.

Light current 18:46, 3 August 2005 (UTC)

What don't you understand? It seems relatively clear to me. Please don't delete things like this. - Omegatron 18:57, August 3, 2005 (UTC)

Should we revert back to the original version?? Rohitbd 15:18, 4 August 2005 (UTC)

The paragraph's still there. I think it's better now. I'm trying to curb this new(?) user's deletionist tendencies. ;-) - Omegatron 15:59, August 4, 2005 (UTC)

[edit] Class AB Amplifier biassing

Copied from my talk page - Omegatron 16:39, August 4, 2005 (UTC)

Never heard it called a "bias-servo" before. This is a non standard term in electronics and may confuse the readers.Light current 16:06, 4 August 2005 (UTC)

If you follow the link that you have reinstated it lead to a description of a mecahanical servo mechanism. The term 'servo' is not used in electronic circuit design terminology. Light current 16:24, 4 August 2005 (UTC)

It is a standard term in amplifier terminology: google search Again, please don't delete things just because you don't understand them or haven't heard of them. - Omegatron 16:39, August 4, 2005 (UTC)

All the links you have sent either refer to amateur electronics designers or maunufacturers of Hi FI audio amps who are known to have their own (sometimes incorrect) terminlogy. I still maintain that this is not a standard electronics term in the field of electronic circuit design. Can you point to some electronics text books that use this term rather than web sites. As you know, you can find any combination of words you like on the web.Light current 16:53, 4 August 2005 (UTC)

I added "in the field of audio amplifiers". - Omegatron 16:58, August 4, 2005 (UTC)

I'm going to agree to this compromise to save time. But this sort of argument is always likely to start when some user puts in something that is basically not relevant to the topic. Then it has to be fiddled with ad nauseam to get it to fit ( when it shouldnt be ther in the first place). I delete or modify, you revert it . There must be a better way. Are there any sensible suggestions out there try to resolve this inherent problem.??Light current 17:17, 4 August 2005 (UTC)

See projects/articles on ESP web-site for "bias servo". Just because the link to "servo" leads to something that doesn't relate to electronics, it doesn't make the term "bias-servo" incorrect. A servo is anything that uses the output of the system to stabilise the system - so even negative feedback is a type of servo mechanism. Most text books are meant for electronics in general and do not treat audio amplifiers as a special class of electronic circuits, and hence do not have terms specific to audio amplifiers, which are used by professional audio amplifier designers. Rohitbd 19:40, 4 August 2005 (UTC)

In addition, if you delete the link, you force someone else to re-add it later when they make the link target relevant. If you leave the link, people will click on it, see that it's not relevant, and expand on the target article. Deleting the link makes the Wikipedia worse. - Omegatron 20:02, August 4, 2005 (UTC)

Moved from my talk page. Rohitbd 10:40, August 8, 2005 (UTC)

I think I have managed to make it make sense now. Have a look . let me know what U think:)Light current 15:55, 4 August 2005 (UTC)

It's OK now. Thanks :-)

[edit] Infinite power during short circuit?

I reverted your edit to voltage source. The power in a resistor driven by a voltage source is V²/R. As R approaches 0, P approaches infinity. - Omegatron 19:10, August 3, 2005 (UTC)

If the power is infinite, where is it dissipated?? (Not in the resistor: that is zero and P=I^2*R)

Also, when shorted, the output voltage is zero, so V^2/R=0 doesnt it?? or does it?

What is 0/0 these days??Light current 19:19, 3 August 2005 (UTC)

Obviously such a circuit cannot exist, since the rule about the voltage across a resistor conflicts with the rule about the voltage across a voltage source. But take the limit of the power function as R approaches zero:

(1 V)²/1 Ω = 1 W
(1 V)²/0.1 Ω = 10 W
(1 V)²/0.01 Ω = 100 W
(1 V)²/0.001 Ω = 1000 W
(1 V)²/.000000000001 Ω = 1000000000000 W

It's obvious that the power dissipated in the resistor increases as the resistance decreases, which is all we can really say since such a circuit cannot exist. It's just the value of y(x) = 1/x for x=0. It's definitely not 0. - Omegatron 19:57, August 3, 2005 (UTC)

Having pondered this question over a few pints of fizzy coloured liquid, I now see that we are BOTH RIGHT and BOTH WRONG at the same time. I'm afraid that we have both fallen into the trap of considering the paradox of the Irresitible Force against the Immovable Object. Neither can win. Neither of us can win. What we need here is a compromise solution that is satisfactory to everyone. I think the clue lies in your statement that both an ideal voltage source AND a perfect short circuit cannot exist. In fact I believe that neither can exist. Hence, we are conducting a sterile argument. I think that the way out of this is to say that an ideal voltage source (or current source for that matter) cannot exist so it is pointless talking abut what happens when they are open or short circuited. We must remove the reference to ideal voltage or current sources that involve calculations of load power from the definitions of voltage source and current source. Is this acceptable to you??:)Light current 22:52, 3 August 2005 (UTC)

[edit] Potential divider "source"??

How can a potential divider be a voltage source?? It is far too dependent on the supply and load resistance/impedance to qualify as a voltage source. In fact the potential divider's o/p voltage is given by,

$V_O = \frac{V_{S}.(R_2 || R_{load})}{R_1 + (R_2 || R_{load})}$

Where R₁ is the upper resistor, R₂ is the lower resistor, R_load is the load connected across R₂, V_O is the o/p voltage across the load and V_S is the supply voltage.

The only condition where the voltage across the load will be constant is when R₁ = 0 and V_S is constant. This only implies no potential divider!!

Rohitbd 13:37, 5 August 2005 (UTC)

Nevertheless a potential divider is very commonly used as a practical voltage source in electronic circuitry where a zener or voltage reg would be too expensive. THe fact that it may have a high Rout and is not as stable as other sources is niether here nor there. I think it does fit within the description (if the divider is supplied by another constant voltage source). If this is removed then all the other examples of practical voltage sources should go because they are not ideal. I think it is te definition that needs changing to cover both ideal and practical sources. Shall we amend to say "when supplied by a source of constant voltage"? These ARE used so please do not delete , modify instead (as someone once told me):-))Comments?? Light current 15:57, 5 August 2005 (UTC)

I also disagree with a voltage divider being classified as a source. Any circuit containing an impedance can be thevenized into a voltage source and series impedance, including any of the circuits from current source. But we call them current sources because they approximate the behavior of an ideal current source. A voltage divider does not approximate the behavior of an ideal voltage source (0 output impedance). - Omegatron 16:07, August 5, 2005 (UTC)

THe title of the page is 'Voltage Sources' (not ideal voltage sources). A potential divider is a source of voltage ( not perfect, but then none are)commonly used maybe just as much as zener source, or amplified diode (neither of these is perfect either. So what have you got agaist the humble divider. Would the person who deleted it please reinstate this device ASAP until agreement has been agreed. on it. DO NOT DELETE MODIFY Light current 17:15, 5 August 2005 (UTC)

It doesn't behave very similarly to a voltage source, though. It's really not the same as a battery or generator or zener source.

I didn't delete it, silly; I moved it here ⇓ ⇓ ⇓ :-) - Omegatron 17:30, August 5, 2005 (UTC)

Removed to talk:

[edit] Potential divider source

Ok lets leave it as I wrote it and see if anyone else wants to comment before I modify it some more before reinserting.Light current 17:41, 5 August 2005 (UTC)

I already modified it before I moved it here. Your version was this:

A simple way of achieving a voltage source is by means of a potential divider applied to another voltage source. The voltage is available across the lower of the two resistors. The source resistance of the source is then R1 in parallel with R2. To achieve a low output impedance at high frequencies, a capacitor can be connected across R2.

You should not have modified it before moving it here: Your version is this:

A simple way of achieving a desired voltage is by means of a potential divider applied to another voltage source. The voltage is available across the lower of the two impedances. The source impedance of the source is then R1 in parallel with R2. If using resistors, a capacitor can be connected across R2 to achieve a low output impedance at high frequencies. The output voltage will vary depending on the load, and will exhibit any non-idealities of the actual source, so this isn't very close to an ideal voltage source.

Let the readers decide which is better. I repeat, the page title is NOT IDEAL voltage sources is it, so why should it have to refer only to ideal sources. THe other sources quoted are not ideal. Can you not see this?? Light current 18:28, 5 August 2005 (UTC)

None of those sources are ideal. But they are designed to approximate an ideal source. A voltage divider is not. I don't think this section should even be in the article, your version or mine. - Omegatron 21:19, August 5, 2005 (UTC)

You did not have a version until I wrote the original! Please stop playing with words and reinstate this para before we get into an edit war. Light current 23:29, 5 August 2005 (UTC)

Why is it relevant that I edited the paragraph before deciding it shouldn't be there? - Omegatron 00:20, August 6, 2005 (UTC)

Some time ago you wrote: to me :

In the future, when you feel like deleting something (other than obvious vandalism or nonsense), please copy and paste it to the talk page and mention why you deleted it, or better yet, ask on the talk page if it should be deleted in the first place. - Omegatron 15:44, August 3, 2005 (UTC)

Why don't you follow your own rules?? This includes removing things from the active poage to the talk page. That is equivalent to deletion in a readers eyes becaus it is not there on the page they have dialled up!!Light current 23:42, 5 August 2005 (UTC)

I followed my rules exactly! :-) I cut and pasted it to the talk page and then mentioned why I thought it should be deleted. How did I not do that?

Yes, it is deleted from the reader's view, for things like this that a person doesn't think belongs in the article, but wants some input on before deleting it entirely. - Omegatron 00:09, August 6, 2005 (UTC)

Would you like to rephrase the last statement using standard English please?? Light current 00:14, 6 August 2005 (UTC)

Yes, it is deleted from the reader's viewpoint. I think this section should be deleted entirely, but I want to get some input before I do so because it is a "gray area", so I delete it from the article but copy it to the talk page with a comment asking for discussion. This way readers aren't mislead, but there is a chance to talk about it before deletion. - Omegatron 00:18, August 6, 2005 (UTC)

Rewritten substantially para on voltage divider. and reinserted for more comments. BTW is a pot div not also the dual of a resitor current source?. These are certainly used and no one complains about their non ideality. Any way, page now covers both ideal and practical sources so there should be no argument. If it gets bigger it could then be split into Theoretical and Practical (or real world) sources but this may create other difficulties.Light current 18:33, 6 August 2005 (UTC)

The article has always been about ideal and practical voltage sources. Voltage dividers are not either.

What do you mean by "resistor current source"? - Omegatron 20:57, August 6, 2005 (UTC)

What do you mean be 'what do you mean by "resistor current source"? I wolud have thought that every electronics engineer would have heard of a current source made from a highish voltage and a large value resistor. They ere used all the time. I have quoted the case of a current mirror where the 'primary' current is solely defined by the voltage supply and a resistor. Read some books on IC op-amps.Light current 21:22, 6 August 2005 (UTC)

How is that a current source?? That's just a current traveling through a resistor. You're saying that in this circuit:

R_source is a current source? As soon as R_load changes, the current will change. - Omegatron 22:05, August 6, 2005 (UTC)

If Rsource is much larger than Rload then, yes, it behaves as a current source in conjuction with the power supply: (everything needs a power supply: even the transistor source, zener diode source etc).If Rload changes , the current changes but not much if RS>>RL. I didnt say it was an Ideal source!!

And in the case of Rload being zero, it is an ideal I source.Light current 22:19, 6 August 2005 (UTC)

That's not a current source; it's a resistor. Likewise a voltage divider is not a voltage source, ideal or otherwise. - Omegatron 13:26, August 7, 2005 (UTC)

If you dont think a potential divider should be included in voltage sources,then ALL other practical votage sources should be removed to their own page. How can you discriminate between a zener voltage source (dependent for operation on supply voltage) with a divider (also dependent on supply voltage )?? Remember we are talking about PRACTICAL sources, not theoretical ones. Just take some time to think about it before replying (PLEASE!!)Light current 20:13, 7 August 2005 (UTC)

Ideal voltage source - maintains constant voltage regardless of loading
Zener voltage source - approximates an ideal voltage source by maintaining constant voltage regardless of fluctuations in Vs or changes in load resistance R2
VBE multiplier voltage source - approximates an ideal voltage source by maintaining constant voltage regardless of fluctuations in Vs or changes in load resistance
Voltage divider - Output voltage changes proportionally to changes in Vs or load resistance - Omegatron 20:39, August 7, 2005 (UTC)

[edit] "Battery" or "cell"?

Changed "battery" to "cell" - cells are what batteries are made of and are the basic voltage sources. This is more a terminology related issue and both terms are often used interchangeably.

[edit] Title of Page

Could people interested in this page please decide whether thry want to call it voltage sources or ideal voltage sources as this affects the content that we are now arguing about. If the page title is Ideal voltage sources I have no objection to the para on potential diveders coming out as long as the paras on zener voltage sources , vbe multipiers etc also come out. On the other hand, if this page is about voltage sources in general, then all the sources above should be included. Can we have some comments PLEASE. Light current 00:36, 6 August 2005 (UTC)

There's not enough information to split it. It should be called Voltage sources and treat both in the same article. - Omegatron 01:41, August 6, 2005 (UTC)

[edit] Mains Electricity

This is the most familiar form of AC voltage source known to the Western world. Generally its output impedance is very low (much less than one ohm).

Mains electricity is a source of electrical power (voltage & current). But I think this article deals with voltage sources used within (and in the context of) electronic circuits. So IMHO, mains electricity should not be included in this article (as also cell or battery). These could be included under perhaps a "sources of electrical power" article.

In addition, what is the relevance of "the western world" here?? Rohitbd 20:30, August 6, 2005 (UTC)

IT may not be the most familiar source of AC to some people living in under developed parts of the world such as Africa, India, China etc. etc but I did not want to say 'civilsed' world as that may be offensive to some.Light current 20:42, 6 August 2005 (UTC)

[edit] Neutrality

Who put this neutrality warning on? THis is inappropriate as this article is not showing any bias on way or the other. Is this what Wikis do when they cant win an argument any other way?Light current 21:55, 6 August 2005 (UTC)

Check the edit history to see who put it there.

Yes, this is what we do when there is a dispute about which content belongs in a page. We don't want to mislead readers. - Omegatron 22:00, August 6, 2005 (UTC)

This is the most familiar form of AC voltage source known to the developed world

Again, what is the relevance of "developed world" to voltage sources? Does it add any value to the article? Information presented on wikipedia is supposed to be neutral, and this particular statement is NOT neutral. Light current, please get consensus from atleast 3-4 more wiki-users or else I will mark that portion as "npov".

Is this what Wikis do when they cant win an argument any other way?

What's this? Why are you taking things personally? We are supposed to present information in as unbiased a way as possible, and it's not to be taken personally if someone disputes what you have written. After all, you yourself would like to question/change/delete what others have written, isn't it? Rohitbd 09:45, August 7, 2005 (UTC)

Moved from my talk page. Rohitbd 10:41, August 8, 2005 (UTC)

I really do not understand what your objection to this article is. Please modify the bit you find not to have NPOV and I will see if I agree or not.Light current 21:49, 7 August 2005 (UTC)

I do not have objection to the article - just to the particular statement that says "...in the western world..." or "...in the developed world...". It does not add any value to the article and is not at all relevant to "voltage sources". Yes, mention of "western world" or "developed world" has meaning in the articles that deal with, say, the history of technological development in the world - but in this case too, accepted international norms of referring to different countries or country groups must be used.

[edit] Sources used in electronic circuitry

Many techniques for producing sources of emf in electronic devices/circuits exist.

Suggest re-wording the statement. All electronic voltage sources (other than mains, batteries) convert some voltage (from a battery or main) to a lower, constant level - and most are used as regulators or references. Should the statement be re-worded to something like -

Many techniques to derive fixed voltages in electronic devices/circuits exist. Circuits which do this are known as "voltage sources" if the voltages are at low currents and "voltage regulators" if voltages are at high currents. The distinction between the two is, however, not very well-defined.

I like the first bit of your sugesstion (up to voltage sources). I dont agree with regs only being used for high current though. This sort of phrasing may have promise if you can develop it further:-)Light current 18:59, 8 August 2005 (UTC)

I did not say that regs are only for high currents - I said that they are called regulators if currents are high - technically the difference is little. In fact we could club linear voltage regulators and constant voltage sources under the same class. But we do have some sort of differentiation between them when we think about them, isn't it? For example, for a PSU what would one prefer - Voltage source or voltage regulator? IMO the difference has more to do with the power the particular source or regulator deals with.

[edit] Capacitor as voltage source

A capacitor (esp large ones)can act and be considered as a voltage source. Especially the super capacitors whic act more like batteries (cells). By duality it is evident that an inductor also can act as a current source ( not ideal- but hey what is??)Comments please to my talk or here Light current 16:08, 8 August 2005 (UTC)

[edit] Introductory para

A voltage source is any device or system that produces or can produce an electrical potential difference.

IMHO, this statement is not entirely correct - the only devices that produce an electrical potential difference are alternators or generators and electrical cells (batteries, solar cells, etc.). A PSU also does not produce EMF - it only transforms the mains to a usable level, though it can still be called a producer of EMF. In the context of electronic circuits and the voltage sources depicted in this article, most only derive a (fixed) voltage from the power supply and as such cannot be termed as producing EMF.

Suggest rewording to -

A voltage source is any device or system that produces an electrical potential difference between it's terminals OR derives a fixed voltage (potential difference) from the power supply. A true voltage source does not need external power to operate, whereas most electronic voltage sources (as depicted in this article) require an external power source and hence are not true voltage sources. They are, however, still termed as "sources" in electronics terminology.

Also, mains supply, batteries, etc may be clubbed under "sources of electrical power" or something of that sort.

Rohitbd 09:27, 9 August 2005 (UTC)

That looks good (apart from the apostrophe). As for the rest of the article, the middle section seems to belong under voltage regulator, not voltage source. I say we move it there. --Heron 11:32, 9 August 2005 (UTC)

Changed the introductory para as above. Which particular item belongs under voltage regulator? The zener voltage source? That circuit already appears in the linear regulator article (which in turn is a sub-article of voltage regulators), and IMO is a boundary case between a voltage source and a voltage regulator. If wee look at it, any voltage regulator is a voltage source and that would include regulated power supplies too. Rohitbd 12:48, August 9, 2005 (UTC)

I don't understand the relevance of "A true voltage source does not need external power to operate, whereas most electronic voltage sources (as depicted in this article) require an external power source and hence are not true voltage sources." - Omegatron 13:05, August 9, 2005 (UTC)

Remember what your Mommies said: "You'll make it worse if you keep picking at it!!" Light current 13:56, 9 August 2005 (UTC)

Huh??

A source supplies voltage or current. There's no such thing as "a source that requires an external source to operate". How is that a source??

An example of such a device is a regulator. A regulator is not a source. It's a regulator. It regulates an external source. - Omegatron 15:31, August 9, 2005 (UTC)

I think we first need to get consensus on the scope and context of the term "voltage source" here. I mean anything can be a voltage source if we look at it that way. We need to put limits on what can be termed as a voltage source in the context of electronic circuits, electricity and usage, and after that decide what should appear in this article and what must be moved to a separate article. Rohitbd 15:25, August 9, 2005 (UTC)

You may recall( if not its up here ^ under Title of Page), R, that I suggested this course of action in the early hours of Aug 6th. This suggestion was rejected at the time and now with all the extra material in this article it is going to be more difficult to sort it.

When I was at school being taught how to write a report, or essay, I was told to jot down a list of headings of what to talk about (then maybe sub headings). I think that was good advice -- it helps to focus the mind properly and saves time. If you put any old stuff in a random order on a page it is a heck of a job later to sort it into the proper categories. This is what has happened on this and other pages on WP especially when more than one person is contributing material. PS Can you please sign your name when adding to talk pages. THanks Light current 19:49, 9 August 2005 (UTC)

[edit] Two voltage sources connected in parallel

What would happen if two voltage sources are connected in parallel? The use of superposition theorem indicates that the output voltage across the paralel combination would be zero. But how does it happen? What is the physical reason behind such a behaviour?

You can't use the superposition theorem for this case. The theorem requires you to replace each source in turn with a short circuit, which is impossible since you would be shorting out the opposite source, which is a fictional component with zero impedance. Since in this case you can't physically do what the theorem requires you to do, it won't give you a meaningful answer. In reality, two equal voltage sources in parallel would look exactly like one source on its own, and two unequal voltage sources in parallel would add up to a puddle of molten copper. --Heron 20:11, 29 January 2006 (UTC)

When two perfect voltage sources are paralelled. the superposition theorem DOES NOT indicate the voltage would be zero, it leads to an irresistable force/immovable object type problem! ofc this is not a problem in real cuircuit design as neither the iresistable force (perfect voltage source) or immovable object (zero resistance connection) can exist in practice. Plugwash 05:11, 3 February 2006 (UTC)

Superposition cannot be applied for ideal sources. For two equal (ideal or non-ideal) sources, the current flow between the sources will be zero. For unequal sources, a current limited by the internal resistancs will flow till the voltages equalise to that of the lesser source's level. If the internal resistances are zero (i.e. in ideal case), theoretically there will (or should) be melt-down (infinite current). Rohitbd 17:56, 5 March 2006 (UTC)

[edit] Combinations and simplifications

I think this page should have a section on how voltage sources can be combined. For example, sources in series can be added together. What I'm not sure about is how or if one can combine voltages sources that are in parallel and in series with elements (like source V1 in series with R1, and those two in parallel with V2 and R2). 68.6.112.70 06:06, 26 May 2006 (UTC)

[edit] New structure

Hi everybody! Two monhts ago, I placed a link on constant current source page pointing to my story about this subject. In this way, I tried to resume the discussion about constant current source and the dual voltage source. Browsing through these and talk pages I found a lot of brilliant thoughts. Only, the pages look quite cluttered; there isn't good structure and hierarchy in their arrangements. So, I suggest rearranging the materials according to the principles below:

1. At every page, expound the subject step-by-step by moving from simple to complex (imperfect to perfect, passive to active, transistor- to op-amp versions etc.)

2. At every step, first reveal the basic circuit idea; then show the concrete circuit solution.

In order to illustrate my suggestion, I have made a web page containing two versions of the contents - a short and a long one. Here is the short version:

Current Source

1. Theoretical current source.
1.1. Ideal current source: definition, examples of natural current sources.
1.2. Comparison between current and voltage sources.
1.3. Real current source: imperfections.

2. Practical current sources.
2.1. Ohmic resistor current source. Imperfections.
2.2. Dynamic resistor current sources.
2.3. Current sources with compensating voltage.
2.4. Current sources with compensating current.
2.5. Current sources using negative feedback.

Voltage Source

1. Theoretical voltage source.
1.1. Ideal voltage source: definition, examples of natural voltage sources.
1.2. Comparison between voltage and current sources.
1.3. Real voltage source: imperfections.

2. Practical voltage sources.
2.1. Voltage divider source. Imperfections.
2.2. Dynamic resistor voltage sources.
2.3. Voltage sources with compensating negative resistance.
2.4. Voltage sources using negative feedback.

I realize that I have proposed major changes in the structure of these pages. So, I would like first to coordinate them with you, especially with those who are created these pages; then, I will try to modify gradually (in small steps) the pages. But yet, don't remember that I am a Wiki newbie; so, don't bite me desperately:) --Circuit-fantasist 07:05, 30 June 2006 (UTC)

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