Logic Gate

Digital Logic

Logic Gates

 Logic gates is an elementary building block of a digital circuit. Logic gates process signals which represent true or false. Normally   the positive signals which represent true or false. Most of the logic gates have two inputs and one output.

AND Gate

                                        

AND gate

• The output of AND gate is TRUE only when all its inputs are FALSE(i.e. even if one input is FALSE, Output will be FALSE).
• Algebraic expression:

Output = AB or Output =A . B

OR Gate

       

    OR Gate

•   The output is true if input A or input B is TRUE.
•    Algebraic expression:

     Output = A + B

NOT Gate

                             

                                                   NOT Gate

NOT Gate

•   NOT gate also know as an inverter.

•   Output is TRUE when input A is FALSE, the output is the inverse of the input

• Algebraic expression :

Universal Gates

A universal gate is a gate which can implement any Boolean function without need to use any other gate type. There are two universal gates NAND Gate and NOR gate.

NAND Gate

          

                                




  NAND Gate

•   The NAND gate operates as an AND gate followed by a NOT gate.( NAND = NOT AND) 

• The output of NAND gate is TRUE when any one of its input is FALSE (i.e. even if one input is FALSE, Output will be TRUE)

• Algebraic expression : 

NOR Gate

                                

                                 


 NOR Gate

•    The NOR gate is a combination NOT gate followed by OR gate. (NOR = Not OR)
•    The output of NOR gate is TRUE when any all its inputs are FALSE (i.e. even if one input is TRUE, output will be FALSE).
•  Algebraic expression :