A logic gate is an idealised or physical device implementing a Boolean function, that is, it performs a logical operation in one or more logical inputs and produces a single logical output.
The logic gates can be classified as
- NOT, AND, OR are basic gates.
- NAND, NOR are universal gates.
- EXOR, EXNOR are an arithmetic circuit or code converter or comparators.
NOT Gate (Inverter)
Truth Table for NOT Gate:
Circuit Symbol for NOT Gate:
Truth Table for AND Gate:
Circuit Symbol for AND Gate:
Properties of AND logic:
- Commutative Law: AB = BA
- Associative Law: ABC = (AB) C = (AC)B = A(BC)
Circuit Symbol for OR Gate:
Properties of OR logic:
- Commutative Law: A + B = B + A
- Associative Law: (A + B + C) = (A + B) + C = A + (B+ C)
Circuit Symbol for NAND Gate:
Circuit Symbol for NOR Gate:
- NOR gate follows commutative law but not follow associative law
Circuit Symbol for EXOR Gate:
Properties of EXOR Logic:
- Enable input = 0
- Disable input = 1
- It is also called stair case switch.
- It is widely used in parity generation and detection.
- When both the inputs are different, then output becomes high or logic 1.
- When both the inputs are same, then output becomes low or logic 0.
Circuit Symbol for EX-NOR Gate:
Properties of EXNOR Gate:
- Enable input = 1
- Disable input = 0
- When both the inputs are same, then output .becomes high or logic 1.
- When both the inputs are different, then output becomes low or logic 0.
Logic Gate Conversions
- OR Gate using NAND Gate:
- AND Gate using NOR Gate:
- NAND Gate using NOR Gate
- NOR Gate using AND Gate
NAND and NOR Gate as Universal Gate
Designing different gates using NAND Gate as Universal Gate:
(i) NOT Gate:
(ii) AND Gate:
(iii) OR Gate:
(iv) EXOR Gate:
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