Introduction: OR Gate From NAND Gate
Sometimes when you're building circuits, you dont always have the right components. Fortunately when it comes to digital logic gates, you can make the component you need! If you're fresh out of OR gates, but have some NAND gates laying around, you're in luck! With three NAND gates, you can construct an effective OR gate! This can be done with the circuit outlined in the attached photograph.

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2 Comments
10 years ago on Introduction
in an emergency you can also use diodes
11 years ago on Introduction
You should combine your NAND-gate instructables into a single one titled something like "implementing other logic functions with nand gates." After all, you can implement ANY logic function with enough NAND gates (or with NOR gates, for that matter.)
Also, some additional explanation (truth tables, quoting Demorgan's theorems, etc) would be nice.
I once bought a lot of NAND gate chips, based partially on this principle.