For example, I have a 3.3V regulator using 5V input from a USB port. I use that output 3.3V rail all over my schematic.

Sure, I can read the entire schematic and see - yep, that's the output. But is there a graphic or unique symbol that indicates that this output is the "source" of the 3.3V rail, and this USB connector pin is the "source" of the 5V and everything else receives it - something like input/output symbols on pins?

Just looking for best practices. Thanks!

  • \$\begingroup\$ You can use the same graphic power rail symbol with different text/net name over it. \$\endgroup\$
    – Eugene Sh.
    Dec 7, 2021 at 17:40
  • \$\begingroup\$ you could have the power supply circuits in a separate section of the schematic diagram \$\endgroup\$
    – jsotola
    Dec 7, 2021 at 17:46

1 Answer 1


I couldn't say if there is a single "best practice" - in fact there are many standards and different companies may adopt or enforce whatever suits them best.

But I can provide at least one example:

Power and Ground Connector Example

Inputs, such as VCC, have traditionally been drawn as arrows in many schematics, but a number of symbols can be used.

In my schematic, I use an arrow to indicate inputs to a device, such as a regulator or IC. (The arrow points in the opposite direction from what one might initially expect.) I use a circle to indicate outputs. A circle can also represent a terminal or post, but in this case it merely serves a visual purpose. (For me at least, the circle visually looks like an "O" and I associate it with "output.")

Depending on your CAD software, the symbol used may or may not alter how it connects to other nodes of the same name. In Altium, with the settings I am using for most projects, the symbol is unimportant, while the net name determines connectivity. Thus, I can use VCC_OUT elsewhere with an arrow as an input, and the output of this example connects.

Example showing connectivity

Of course, I wouldn't name the nets in this way. They are usually something like VCC_5V0 or VCC_IO, etc.

  • \$\begingroup\$ Thank you for sharing! That's exactly the kind of system I was looking to implement. That's much cleaner than the 0-ohm resistors between the source and the net I've used in the past. \$\endgroup\$
    – vkaiser
    Dec 9, 2021 at 0:50

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