What are Universal Gates Why They are Called So?

Simply in digital logic, a universal logic gate is a logic gate that can be used to construct all other logic gates like AND, OR & NOT. These basic gates can be represented or created with the help of universal digital logic gates.

NOR gate – Universal Logical Gate

It is the combination of NOT and OR gate in such a way that output of OR gate is connected to the input of the NOT gate.   To talk about its input and output this will take one or multiple inputs but the output of the gate is high only when the input is low. Hence its outputs are the reverse of OR gate.  

Truth Table   Input               Output A      B            Y=(A.B)’

0 0    1        

0       1             0

1       0             0

1       1             0

Boolean Equation Y = (A.B)’

NAND Universal Logic Gate

It is the combination of NOT and AND gate in such a way that output of NAND gate is connected to the input of the NOT gate.   The output of this gate is low only when all inputs are high. Hence this gate is a reverse of AND gate.  

Truth Table   Input               Output A      B            Y=(A.B)’

0       0             1

0       1             1

1       0             1

1       1             0  

Boolean Equation   Y = (A.B)’