Question

1. Briefly explain logic gates and various gates used in digital logic design.

Answer 1

Logic Gate :

They are basic building blocks of any digital system., they can have more than one input or may be 1.and only 1 output,it can be made from resistors,transistors ,diodes.It is a small transistor circuit which implements in different forms.It operates in two voltage called logic 1 and logic 0.

1. AND gate - Gives an output of 1 if both two inputs are 1,it gives 0 otherwise.

X	Y	F
0	0	0
0	1	0
1	0	0
1	1	1

2. OR gate - Gives an output of 1 if either of two inputs are 1,it gives 0 otherwise.

x	y	F
0	0	0
0	1	1
1	0	1
1	1	1

3. NOT gate - The NOT gate gives an output of 1 if input is 0 and vice versa.

x	F
0	1
1	0

4. XOR (Exclusive-OR) gate : - The XOR gate gives an output of 1 if either both inputs are different , it gives 0 if they are same.

x	y	F
0	0	0
0	1	1
1	0	1
1	1	0

5.NAND gate :- The NAND gate gives an output of 0 if both inputs are 1 ,it gives 1 otherwise.

x	y	F
0	0	1
0	1	1
1	0	1
1	1	0

6.NOR gate :- The NOR gate gives an output of 1 if both inputs are 0,it gives 0 otherwise.

x	y	F
0	0	1
0	1	0
1	0	0
1	1	0

7 . XNOR (Exclusive NOR) gate :- The XNOR gate gives an output of 1 if both inputs are same and 0 if both are different .

x	y	F
0	0	1
0	1	0
0	0	0
0	1	1

Out of the seven logic gates NAND and NOR are also known as universal gates because they can be used to implement any digital circuit without using any other gate.