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Logic Gates

Logic gates give an output depending on the condition of the inputs. Below are the symbols and truth tables for the common types of logic gates. Note that due to font limitations the Boolean symbol for XOR expressed here as (+) is actually a + sign inside a circle.

AND:

A B Output AND Gate
0 0 0
0 1 0
1 0 0
1 1 1
Expression: Output = A.B

OR:

A B Output OR Gate
0 0 0
0 1 1
1 0 1
1 1 1
Expression: Output = A+B

XOR:

A B Output XOR Gate
0 0 0
0 1 1
1 0 1
1 1 0
Expression: Output = A(+)B

NOT:

Input Output NOT Gate
0 1
1 0
Expression: Output = Input

NAND:

A B Output NAND Gate
0 0 1
0 1 1
1 0 1
1 1 0
Expression: Output = A.B

A NOT gate can be formed from a NAND gate by connecting A and B together.

NOR:

A B Output NOR Gate
0 0 1
0 1 0
1 0 0
1 1 0
Expression: Output = A+B

A NOT gate can be formed from a NOR gate by connecting A and B together.

XNOR:

A B Output XNOR Gate
0 0 1
0 1 0
1 0 0
1 1 1
Expression: Output = A(+)B

A NOT gate can be formed from an XNOR gate by connecting one input to ground.

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