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What I want to create is a simple logic gate that doesn't actually perform any logic, but instead simply repeats the given signal. I want to do this so that I can have a one-way wire.

Some ideas that I've thought of, but I'm not sure if they're efficient, or which one is more efficient:

  • A NOT gate plugged into a NOT gate.

  • An AND gate with both of the inputs as the same wire

  • An OR gate with both of the inputs as the same wire.

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    \$\begingroup\$ You mean a buffer? \$\endgroup\$
    – Oldfart
    Sep 11, 2019 at 16:11
  • \$\begingroup\$ What is a "one-way wire"? \$\endgroup\$
    – Transistor
    Sep 11, 2019 at 16:18
  • \$\begingroup\$ A one-way wire would be equivalent to the above examples of two NOT gates or the AND/OR gates. In Minecraft-speak, a redstone repeater, except I'm not using Minecraft. \$\endgroup\$
    – Aaron Franke
    Sep 11, 2019 at 16:19
  • \$\begingroup\$ @AaronFranke just look for "logic buffer" or "buffer gate" as Oldfart said \$\endgroup\$
    – MrBit
    Sep 11, 2019 at 19:07

2 Answers 2

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What you're looking for is commonly known as a "buffer". Any of your proposed constructions would work to form one; I believe the two-cascaded-NOT-gates is common in CMOS logic.

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  • \$\begingroup\$ Having spent time looking at chip schematics in my youth -- in something like 4000-series or 74Cxx series, a buffer is two cascaded inverters, as you say. 74HCxx and 'fancier' logic have three stage inverters (e.g. the 74HC04), and just add another internal stage for a buffer. \$\endgroup\$
    – TimWescott
    Sep 11, 2019 at 17:18
  • \$\begingroup\$ A buffer may be more than two inverters, as long as there are an even number. Buffers that drive heavy loads often need more than two stages to increase the drive levels while minimizing the added propagation delay. \$\endgroup\$
    – Elliot Alderson
    Sep 11, 2019 at 17:23
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Buffers are another option, but really "one way" is the default of logic signals. You do have exceptions where tri-state gate outputs are connected together, wired "OR" and perhaps some other exceptions.

The buffer or non-inverting gate construct will delay the signal by a bit and might provide stronger drive, which are useful in some circumstances. Sometimes you want true and complementary outputs that change at almost the same time, such as this one.

enter image description here

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  • \$\begingroup\$ But what if I have one of my input lines directly wired to one of my outputs, yet that input line is also used elsewhere? Wouldn't that cause issues if you put electricity to that output wire? \$\endgroup\$
    – Aaron Franke
    Sep 11, 2019 at 16:16
  • \$\begingroup\$ Usually one output can drive many inputs. If you're taking it into a situation (eg. off-board) where a user can abuse it by say shorting it, then you might want what you describe. In such a case you might not want a buffer (at least not without some protection such as series resistance and clamps) because the short-circuit current of a buffer with large fan-out will tend to be much higher and it would be more likely to fail from overheating. \$\endgroup\$
    – Spehro Pefhany
    Sep 11, 2019 at 16:17
  • \$\begingroup\$ This is a pretty important point that I probably should have mentioned in my answer, really. Good answer. \$\endgroup\$
    – Hearth
    Sep 11, 2019 at 20:23

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