Timeline for Where does this current source symbol come from?
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| May 10, 2018 at 22:59 | comment | added | horta | @Felthry Usually you'll see the current direction arrow and the amount of current mirrored in the diagrams next to the symbol so putting the diagram flipped 90 degrees would take even more space. This is logical speculation at this point. static.righto.com/images/lm308/LM108_classic_simplified.png | |
| May 10, 2018 at 20:40 | comment | added | AlmostDone | Thinking back, I believe my first impression suggested the symbol for infinity, as in infinite internal resistance. | |
| May 10, 2018 at 20:24 | comment | added | Hearth | @horta surely that would be sideways compared to this, though? | |
| May 10, 2018 at 18:26 | comment | added | horta | @Felthry Here's a basic current mirror. en.wikipedia.org/wiki/Current_mirror#/media/… The next level of simplification is to convert both transistors to circles and add a dashed line in between to show that they are mirroring the current. The last level of simplification is to just draw two overlapping circles representing a derived current source. | |
| May 10, 2018 at 17:05 | comment | added | Hearth | @horta "because the original halfway expanded version..." this sentence doesn't parse right to me, I don't understand what you're trying to say. | |
| May 10, 2018 at 16:57 | comment | added | horta | @ThePhoton I totally agree with you. The current meaning for those not familiar with the origins nor actively using it for analog IC design will be just "current source" and no one will really misunderstand the effect of the symbol in the diagram since at the end of the day, even in a mirrored config, it's acting simply as a current source. | |
| May 10, 2018 at 16:55 | comment | added | The Photon | If there's a spec from IEC or somebody that says "use this symbol for a current mirror and that symbol for other kinds of current source" that would at least be evidence that somebody is trying to hold the line on the original meaning. | |
| May 10, 2018 at 16:53 | comment | added | The Photon | @horta, kind of like the English language, what the symbol means depends on what people use it to mean. If people use the word "literally" to mean "metaphorically", then "literally" literally comes to mean "metaphorically". | |
| May 10, 2018 at 16:53 | comment | added | horta | @Felthry Because the original halfway expanded version is the actual current source image on one vertical path with the current source reflection being on another vertical path with a dashed line connecting them. I don't know if I'm answering your question though. Two circles overlapping eachother is a small concise way to represent two linked current sources/sinks. | |
| May 10, 2018 at 16:51 | history | edited | Neil_UK | CC BY-SA 4.0 |
grocer's apostrophe
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| May 10, 2018 at 16:46 | comment | added | Hearth | So if this is the case, why is it shown as two overlapping circles? Where does that particular glyph come from? | |
| May 10, 2018 at 16:41 | comment | added | horta | @ThePhoton I would argue, this question itself is an example of how people may have misunderstood the origins of the symbol since it's mostly used showing the mirrored current side (vs the original mirroring current). There's no reason to assume a textbook or it's authors are flawless. In college, we were given bonus points to point out flaws in the textbook. | |
| May 10, 2018 at 16:28 | comment | added | The Photon | I've seen it used as a pure current source. For example, in a noise model of a photodiode, in a textbook from a major academic publisher. | |
| May 10, 2018 at 16:15 | history | answered | horta | CC BY-SA 4.0 |
