# Can you connect an output from a logic gate to 2 or more logic gates or inputs?

The second XOR gate looks like its output is being connected as inputs of 2 different gates at the same time. Am I interpreting this incorrectly or is it possible to send the a single output to 2 gates simultaneously?

• It is definitely possible (and required in many designs) to connect the output of a gate to the inputs of several other gates. The only limitation is electrical. If this number is to high, gate performances can be degraded. If interested, you can check en.wikipedia.org/wiki/Fan-out – Alain Merigot Jan 18 '19 at 10:08
• This seems more suited to Electrical Engineering. – Yuval Filmus Jan 18 '19 at 12:51
• Questions should be self-contained. Please do not simply add a link to an image; insert the image as such directly in the question instead. Thank you. – dkaeae Jan 18 '19 at 13:39

In circuit complexity, the fan-out of a gate is the number of gates its output is connected to (similarly, the fan-in is the number of inputs to the gate). A circuit in which all gates have fan-out 1 is known as a formula. It is known that some $$n$$-bit functions can be computed by circuits of size $$O(2^n/n)$$ but require formulas of size $$\Omega(2^n/\log n)$$. It is conjectured that polynomial size circuits can compute more functions than polynomial size formulas, but this conjecture, known as the $$\mathsf{NC^1} \stackrel?= \mathsf{P}$$ question, remains unproved.