NOT gate (inverter)
The output Q is true when the input A is NOT true, the output is the inverse of the input:
Q = NOT A
A NOT gate can only have one input. A NOT gate is also called an inverter.
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| Traditional symbol |
IEC symbol |
Truth Table |
AND gate
The output Q is true if input A AND input B are both true:
Q = A AND B
An AND gate can have two or more inputs, its output is true if all inputs are true.
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| Input A |
Input B |
Output Q |
| 0 |
0 |
0 |
| 0 |
1 |
0 |
| 1 |
0 |
0 |
| 1 |
1 |
1 | |
| Traditional symbol |
IEC symbol |
Truth Table |
NAND gate (NAND = Not AND)
This is an AND gate with the output inverted, as shown by the 'o' on the output.
The output is true if input A AND input B are NOT both true:
Q = NOT (A AND B)
A NAND gate can have two or more inputs, its output is true if NOT all inputs are true.
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| Input A |
Input B |
Output Q |
| 0 |
0 |
1 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
0 | |
| Traditional symbol |
IEC symbol |
Truth Table |
OR gate
The output Q is true if input A OR input B is true (or both of them are true):
Q = A OR B
An OR gate can have two or more inputs, its output is true if at least one input is true.
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| Input A |
Input B |
Output Q |
| 0 |
0 |
0 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
1 | |
| Traditional symbol |
IEC symbol |
Truth Table |
NOR gate (NOR = Not OR)
This is an OR gate with the output inverted, as shown by the 'o' on the output.
The output Q is true if NOT inputs A OR B are true:
Q = NOT (A OR B)
A NOR gate can have two or more inputs, its output is true if no inputs are true.
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| Input A |
Input B |
Output Q |
| 0 |
0 |
1 |
| 0 |
1 |
0 |
| 1 |
0 |
0 |
| 1 |
1 |
0 | |
| Traditional symbol |
IEC symbol |
Truth Table |
EX-OR (EXclusive-OR) gate
The output Q is true if either input A is true OR input B is true,
but not when both of them are true:
Q = (A AND NOT B) OR (B AND NOT A)
This is like an
OR gate but excluding both inputs being true.
The output is true if inputs A and B are
DIFFERENT.
EX-OR gates can only have 2 inputs.
 |
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| Input A |
Input B |
Output Q |
| 0 |
0 |
0 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
0 | |
| Traditional symbol |
IEC symbol |
Truth Table |
EX-NOR (EXclusive-NOR) gate
This is an EX-OR gate with the output inverted, as shown by the 'o' on the output.
The output Q is true if inputs A and B are the
SAME (both true or both false):
Q = (A AND B) OR (NOT A AND NOT B)
EX-NOR gates can only have 2 inputs.
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 |
| Input A |
Input B |
Output Q |
| 0 |
0 |
1 |
| 0 |
1 |
0 |
| 1 |
0 |
0 |
| 1 |
1 |
1 | |
| Traditional symbol |
IEC symbol |
Truth Table |
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