I cannot figure out the meaning of the logical OR ( || ) in this context.

Rin = R1 +R2||R4

enter image description here in this circuit

enter image description here

This was taken from this video https://www.youtube.com/watch?v=uir9Js1l_r8

*at around 6:00 of the video

  • \$\begingroup\$ + means series and || or // has an analog meaning not the same as logical OR AND XOR symbols.. 1 / (R2//R4) = 1 / R2+ 1 / R4 (it means parallel ) \$\endgroup\$ Feb 10, 2021 at 18:09
  • \$\begingroup\$ Basic research: google.com/… \$\endgroup\$
    – Andy aka
    Feb 10, 2021 at 18:16

1 Answer 1


It's the parallel equivalent between \$R_2\$ and \$R_4\$. Actually in this circuit it's only valid since \$R_4\$ is much greater than \$R_3\$, so you can ignore \$R_3\$ and end up with \$R_2 ||R_4\$.


Not the answer you're looking for? Browse other questions tagged or ask your own question.