NOR gate

<table><tbody><tr><th colspan="3">NOR gate <a href="/facts/Truth_table/4KsmArDW">truth table</a></th></tr><tr><td colspan="2">Input</td><td>Output</td></tr><tr><td>A</td><td>B</td><td>A NOR B</td></tr><tr><td>0</td><td>0</td><td>1</td></tr><tr><td>0</td><td>1</td><td>0</td></tr><tr><td>1</td><td>0</td><td>0</td></tr><tr><td>1</td><td>1</td><td>0</td></tr></tbody></table>
<p>The NOR (NOT OR) gate is a digital <a href="/facts/Logic_gate/RHLulvKI">logic gate</a> that implements <a href="/facts/Logical_NOR/HKhNW8Qc">logical NOR</a> - it behaves according to the <a href="/facts/Truth_table/4KsmArDW">truth table</a> to the right. A HIGH output (1) results if both the inputs to the gate are LOW (0); if one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the <a href="/facts/Negation/q5AQBvBj">negation</a> of the <a href="/facts/OR_gate/ox2lHgIM">OR</a> operator. It can also in some senses be seen as the inverse of an <a href="/facts/AND_gate/tVKQD0w1">AND gate</a>. NOR is a <a href="/facts/Functionally_complete/ncyHAsHH">functionally complete</a> operation—NOR gates can be combined to generate any other logical function. It shares this property with the <a href="/facts/NAND_gate/g6FUuhJT">NAND gate</a>. By contrast, the <a href="/facts/Logical_disjunction/jbI2EGlM">OR</a> operator is <i>monotonic</i> as it can only change LOW to HIGH but not vice versa.
</p><p>In most, but not all, circuit implementations, the negation comes for free—including <a href="/facts/CMOS/NJIWYgBl">CMOS</a> and <a href="/facts/Transistor%25E2%2580%2593transistor_logic/z4bvHotl">TTL</a>. In such logic families, OR is the more complicated operation; it may use a NOR followed by a NOT.  A significant exception is some forms of the <a href="/facts/Domino_logic/Wo41NVLf">domino logic</a> family.
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NOR gate open-in-new

NOR gate