# DC Analysis of Transistor Circuits - Double vertical line symbol

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

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.

• It's shorthand for "in parallel with" – Finbarr Jun 12 at 10:57
• 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) – Huisman Jun 12 at 11:57
• To avoid confusion: In case of only 2 variables it can be rewritten to (xy) / (x+y) – Huisman Jun 12 at 12:06