Logic Gates

  . These are elementary building blocks of digital circuit.

  . Made by transistors.

  . It has one or more inputs and only one output.

  . Output is active only for certain input combinations.

  . Common logic gates are:

     - AND gate

     - OR gate

     - NAND gate

     - NOR gate

Applications of Logic gates:

    . Used as building blocks in every digital product.

    . Used in multiplexers, Arithmetic and Logic Unit, Computer memory and Registers.

    . Also found in mobiles, calculators, tablets and digital watches etc. 

1. AND gate

    . It has two inputs and one output.

    . Output is active only when both the inputs are active.
    . It can be observed in many home appliances.
    . Example: Washing Machine works only when both power supply and Power ON button turned on.
                      Water flows into bucket only when wall on tank and water tap is open.

    . Symbol and Truth table of AND gate:

2. OR gate

    . It has two inputs and one output.

    . Output is active when either of inputs is active.
    . Example: We can operate TV channels either from remote or buttons on TV.
                      Entering into home from either of doors opened.

    . Symbol and Truth table of OR gate:

3. NAND gate

    . It has two inputs and one output.

    . Works in the opposite function of AND gate.
    . NAND and NOR gates are called Universal gates because we can achieve any other logic gate function using these two.

    . Output is inactive only when both the inputs are active.

    . Symbol and Truth table of NAND gate:

4. NOR gate

    . It has two inputs and one output.

    . Works in the opposite function of OR gate

    . Output is active only when both the inputs are inactive.

    . Symbol and Truth table of NOR gate: