I have stumbled twice across this symbol || being used in the analysis of transistor circuits.

An example can be seen at this address: http://www.learningaboutelectronics.com/Articles/Dc-analysis-of-a-bipolar-junction-transistor-circuit

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I can understand it: x||y = (xy)/(x+y)

But what is it called and why is it used? Because I do not know the name, I was unable to find anything with a search. "Double vertical line transistor circuit analysis" didn't return any results.

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    \$\begingroup\$ It's shorthand for "in parallel with" \$\endgroup\$ – Finbarr Jun 12 at 10:57
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    \$\begingroup\$ Do note \$ a || b || ... || z = 1 / ( \frac{1}{a} + \frac{1}{b} + ... \frac{1}{z} )\$. In case of only x and y it can be rewritten to (xy) / (x+y) \$\endgroup\$ – Huisman Jun 12 at 11:57
  • \$\begingroup\$ To avoid confusion: In case of only 2 variables it can be rewritten to (xy) / (x+y) \$\endgroup\$ – Huisman Jun 12 at 12:06

It's shorthand for "in parallel with", though I've never seen it used before and it's certainly not an accepted mathematical operator.

In many programming languages that would be a logical OR operator.

  • \$\begingroup\$ I think i first came across the notation in some TI literature about opamps, no idea where it comes from though. \$\endgroup\$ – Colin Jun 12 at 11:01
  • \$\begingroup\$ When I first encountered it I thought it was an or operator, but couldn't understand what the meant in the context of a circuit. It makes sense that it means "parallel". I guess this isn't a standard notation then? \$\endgroup\$ – user3728501 Jun 12 at 11:16
  • \$\begingroup\$ Actually, does that make sense? Working through the content on that webpage I find myself completely confused. What does Rb refer to? \$\endgroup\$ – user3728501 Jun 12 at 11:22
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    \$\begingroup\$ The parallel operator || is a mathematical function which is used especially as shorthand in electrical engineering. (en.wikipedia.org/wiki/Parallel_(operator) \$\endgroup\$ – Huisman Jun 12 at 11:52
  • \$\begingroup\$ I have used it for as long as I can remember (~30 yrs). But it is a human shorthand, I don't know of any programming languages that recognize it as parallel. \$\endgroup\$ – Mattman944 Jun 12 at 13:09

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