NOR Gate: The Universal Logic Gate
Similar to NAND, a NOR gate is “universal” because any standard logic gate can be built using only NOR gates.
1. NOT Gate
Connect both inputs of a single NOR gate together to create an inverter.
Output = A + A = A
2. OR Gate
A NOR gate followed by a NOR-based NOT gate (Inverter).
Output = A + B = A + B
3. AND Gate
Invert inputs A and B using NOR gates, then feed them into a third NOR gate.
Output = A + B = A ⋅ B
4. NAND Gate
Constructed by adding a NOR-based NOT gate to the output of a NOR-based AND gate.
Output = A ⋅ B
5. XOR Gate (5 NOR Gates)
Requires five NOR gates to produce logic equivalent to AB + AB.
Output = A ⊕ B
6. XNOR Gate (4 NOR Gates)
Unlike NAND-based logic, XNOR is simpler to build with 4 NOR gates.
Output = A ⊕ B = AB + AB
* Tip: NOR gates are particularly useful for creating “Bubbled AND” logic.
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