Common mode, differential mode: Difference between revisions
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==Theoretical side== | ==Theoretical side== | ||
===Common mode=== | ===Common mode=== | ||
''Common mode signalling'' points at a situation where you have | |||
* a reference conductor, which both ends of this communication have in common | * a reference conductor, which both ends of this communication have in common | ||
:: often called "signal common". | :: often called "signal common". | ||
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Differential subtracts the voltages on two lines, for one resulting signal. | Differential subtracts the voltages on two lines, for one resulting signal. | ||
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There are a few areas where it would've been nice if it were standard - like consumer audio systems. | There are a few areas where it would've been nice if it were standard - like consumer audio systems. | ||
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===Perhaps-necessary clarification=== | |||
====Common mode, differential mode, single ended==== | |||
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Differential mode is a voltage difference | |||
: without tying either to a known level, without a shared reference | |||
: also meaning these wires are dedicated to one signal | |||
Common mode is a voltage difference | |||
: tying one to a known level | |||
: probably a reference reused for multiple signals | |||
Single ended means a signal is present on one wire and not another | |||
: which seems to describe common-mode reality (and the two are used as near-synonyms) | |||
: because yes, common mode basically implies single ended, | |||
: '''but''' single ended can be used on both common mode and differential mode | |||
:: e.g. while introductions to XLR make a big kerfuffle over sending signal/2 and -signal/2 on the two wires, it is ''entirely valid'' to send all the signal on one wire and nothing on the other (which you'd easily call single-ended), because after differential interpretation this implies the same signal, and the differential-based noise reduction is not affected at all. | |||
::: In fact, doing this inside a balanced output driver seems moderately common{{verify}} because it is a little simpler component-wise. <!--{{comment|(It may (or may not) be approximately 3dB {{verify}} quieter, but this is rarely an issue)}} and depending on what you stick after it, there may be no practical difference.{{verify}} | |||
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If a distinction is made between single ended and common mode, | |||
single-ended often refers more to the concept, | |||
common mode more to electrical reality of conductors. | |||
Both single-ended and common mode are mainly contrasted with [[#Differential_mode|differential mode]] | |||
====Differential in more depth==== | |||
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There are some related yet distinct concepts here: | There are some related yet distinct concepts here: | ||
* '''differential signalling''' | * '''differential signalling''' | ||
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===Derived and related terms=== | ====Derived and related terms==== | ||
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Latest revision as of 00:28, 21 April 2024
✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.
Common mode versus differential mode is about communicating a signal electrically, usually as a voltage signal.
Theoretical side
Common mode
Common mode signalling points at a situation where you have
- a reference conductor, which both ends of this communication have in common
- often called "signal common".
- a conductor for a signal
And the signal is the voltage difference between the two.
Differential mode / differential signalling
✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.
Perhaps-necessary clarification
Common mode, differential mode, single ended
If a distinction is made between single ended and common mode, single-ended often refers more to the concept, common mode more to electrical reality of conductors.
Both single-ended and common mode are mainly contrasted with differential mode
Differential in more depth
Practical side
Balanced audio / pro audio
See Music_-_studio_and_stage_notes#Notes_on_balanced_audio
Comparisons
See also