Logic gates are electronic circuits that combine multiple inputs to produce an output. There are several types of logic gates that process inputs differently, including AND, OR, NOT, NAND, NOR, XOR, and XNOR gates. Each gate is characterized by its symbol, truth table that specifies the output for every combination of inputs, and Boolean expression that defines its function.

1. Basic Logic gates
Param Radadiya 1

2. Logic gates are devices that can combine multiple inputs at independent
logic levels and come up with an output accordingly. There are many kinds of
logic gates, and the distinction lies in that each kind processes the inputs
differently, and may give different outputs for the same inputs.
The way the logic gate processes different inputs is given in a truth table
for that gate, which lists all the possible combinations of inputs next to their
outputs. An example is given for a simple one-input gate with the function of
giving the opposite logic level at the output to the one at the input. The inputs
are given on the left, and the outputs are on the right. Generally, the inputs are
called A, B, C, etc., and the output is labelled Q. In this case, there are only two
possible inputs, 1 or 0, but logic gates can have any number of inputs.
Introduction:
Param Radadiya
2

3. ➢ AND gate :
• The AND gate is an electronic circuit that gives a true output
(1) only if all its inputs are true. A dot (·) is used to show
the AND operation i.e. A·B.
• Note that the dot is sometimes omitted i.e. AB
(Symbol)
Input A Input B Output
Y = A∙B
0 0 0
0 1 0
1 0 0
1 1 1
Inputs Output
• Boolean Expression : Y = A∙B
(Truth Table) (Circuit)
Param Radadiya
3

4. ➢NOT gate :
• The NOT gate is an circuit that gives inverse output
of given input.
• It’s also known as an inverter.
(Symbol)
Inputs Output
• Boolean Expression : Y = Ā or Y = A’
Switch A Switch B Output
Y = A+B
0 0 0
0 1 1
(Truth
Table)
(Circuit)
Param Radadiya
4

5. ➢OR gate :
• The OR gate is an electronic circuit that gives a true
output (1) if one or more of its inputs are true. A
plus (+) is used to show the OR operation.
(Symbol)
Inputs Output
• Boolean Expression : Y = A+B
Input A Input B Output
Y = A+B
0 0 0
0 1 1
1 0 1
1 1 1
(Truth Table)
(Circuit)
Param Radadiya
5

6. ➢NAND gate :
•This is a NOT-AND gate which is equal to an AND gate
followed by a NOT gate.
•It’s UNIVERSAL gate.
•The outputs of all NAND gates are true if any of the inputs are
false.
•The symbol is an AND gate with a small circle on the output.
The small circle represents inversion
(Symbol)
Inputs Output
• Boolean Expression : Y = 𝐴 ∙ 𝐵
Input A Input B Output
Y = 𝐴 ∙ 𝐵
0 0 1
0 1 1
1 0 1
1 1 0
(Truth Table)
Param Radadiya
6

7. ➢NOR gate :
•This is a NOT-OR gate which is equal to an OR gate
followed by a NOT gate.
•It’s UNIVERSAL gate.
•The outputs of all NOR gates are false if
any of the inputs are true.
•The symbol is an OR gate with a small circle on the
output. The small circle represents inversion.
(Symbol)
Inputs Output
• Boolean Expression : Y = 𝐴 + 𝐵
Input A Input B Output
Y = 𝐴 + 𝐵
0 0 1
0 1 0
1 0 0
1 1 0
(Truth Table)
Param Radadiya
7

8. ➢EX-OR gate :
• The 'Exclusive-OR' gate is a circuit which will give a
true output if either, but not both, of its two inputs
are true.
• An encircled plus sign (⊕) is used to show the
EXOR operation.
(Symbol)
Inputs Output
• Boolean Expression : Y = A ⊕B
Input A Input B Output
Y = A ⊕B
0 0 0
0 1 1
1 0 1
1 1 0
(Truth Table)
Param Radadiya
8

9. ➢EX-NOR gate :
•The 'Exclusive-NOR' gate circuit does the opposite to the EXOR
gate.
•It will give a false output if either, but not both, of its two inputs
are true.
•The symbol is an EXOR gate with a small circle on the
output.
•The small circle represents inversion.
(Symbol)
Inputs Output
• Boolean Expression : Y =A ⊕ B
Input A Input B Output
Y =A ⊕ B
0 0 1
0 1 0
1 0 0
1 1 1
(Truth Table)
Param Radadiya
9