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AND OR and NAND NOR Functions

Logic Gates

  • A logic gate is a basic building block of a digital circuit that has two inputs and one output.

  • These gates are implemented using electronic switches like transistors, resistors, and diodes.

  • Basic logic gates are built by using MOSFET technology.

Input

Logical

operation

Output

Logic Gate

Input and output have only one nominal state.

  • Low ( 0 volt) = 0 (False)

  • High (5 volt) = 1 (True)

  • The basic logic gates are  AND, OR and NOT. 

  • And all logic gates are categorized into seven:

  • AND

  • OR

  • XOR

  • NAND

  • NOR

  • XNOR

  • NOT 

AND Logic Gate

  • An AND gate can have two or more inputs, its output is true if all inputs are true. The output Q is true if input A AND input B are both true: Q = A AND B

Q

  • Truth table :

  • Switch Representation of the AND Function :

OR Logic Gate

  • An OR gate can have two or more inputs, its output is true if at least one input is true. The output Q is true if input A OR input B is true (or both of them are true): Q = A OR B

Q

  • Truth table :

  • Switch Representation of the OR Function :

  • NAND = Not AND. This is an AND gate with the output inverted, as shown by the 'o' on the symbol output. A NAND gate can have two or more inputs, its output is true if NOT all inputs are true.

  • The output Q is true if input A AND input B are NOT both true: Q = NOT (A AND B)

  • A function in sum of products form can be implemented using NAND gates by replacing all AND and OR gates by NAND gates.

  • The NAND gates are called universal functions since with either one the AND and OR functions and NOT can be generated.

Q

  • Truth table :

  • Switch Representation of the NAND Function :

NAND Logic Gate

  • NOR = Not OR. This is an OR gate with the output inverted, as shown by the 'o' on the symbol output. A NOR gate can have two or more inputs, its output is true if no inputs are true.

  • The output Q is true if NOT inputs A OR B are true: Q = NOT (A OR B)

  • A function in the product of sums form can be implemented using NOR gates by replacing all AND and OR gates by NOR gates.

  • The NOR gates are called universal functions since with either one the AND and OR functions and NOT can be generated.

  • The basic logic gates are used in many circuits like a push-button lock, light-activated burglar alarm, safety thermostat, an automatic watering system, etc.

  • Ex-OR gates are used in the generation of parity generation and checking units.

  • Every integrated circuit uses logic gates to design some specific function.

Q

  • Truth table :

  • Switch Representation of the NOR Function:

NOR Logic Gate

Application

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