LOGIC GATES


1 .Logic gates are used to design digital circuit system.

2. The logic gates are divided into three types. They are:-

                  a. Basic gates
                  b. Universal gates
                  c. Special gates.

3. The basic gates consists of NOT, AND, OR.

4. The universal gates consists of NAND, NOR.

5. The special gates consists of EX-OR, EX-NOR.

6. The truth table is used to represent the input/output combination for every gate i.e. the            truth table is used to represent the output for each gate of possible input combinations.


BASIC GATES :-
                              
In basic gates there are three types of gates.They are:

               a. NOT gate
               b. AND gate
               c. OR gate


a. NOT Gate

  • NOT gate is known as “inverter” i.e. when we give some input to NOT gate then we will get the output in complement form.
Symbol an Truth Table:

              




NOTE:-
  • Here when we give the input 1 we get the output in complement form which is 0.
  • When we give the input zero we will get the output in complement form which is 1.


b. AND Gate
                        
  • AND gate is used to perform logic multiplication.


Symbol an Truth Table:



NOTE:-
  • For AND gate there can be two or more inputs but there will be only one output.



c. OR Gate
  • OR gate  is used to perform logical addition.

Symbol an Truth Table:




NOTE:-
  • For OR gate there can be two or more inputs but there will be only one output.

UNIVERSAL GATES :-

    1. The universal gates are used to build NOT, AND, OR gates.
    2. Universal gates are of two types. They are:

                a. NAND gate
                b. NOR gate

a. NAND Gate
  • The NAND gate is the combination of NOT and AND  gates.
  • NAND gate can be designed by using AND gate with an inverter.

Symbol an Truth Table:



b. NOR  Gate  
  • NOR gate is the combination of NOT and OR gates.
  • NOR gate can be designed by using OR gate with inverter.

Symbol an Truth Table:





SPECIAL GATES :-

    1. There are two types of gates. They are:

         a. Exclusive OR Gate
         b. Exclusive NOR Gate

a. Exclusive OR Gate

Symbol an Truth Table:





a. Exclusive NOR Gate

Symbol an Truth Table:




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