Logic Gates in Digital World

Logic gates are basic building blocks of any digital circuits. Logic gates are electronics device that gives output on the different combinations of digital inputs. Different Logic gates are constructed using different technologies depending on different Logic Family like TTL, CMOS, DTL, ECL etc. Logic Circuits include devices such as multiplexers, registers, memory units, processors, which contains more than 100 millions Logic Gates.

There are total six Logic Gates are available

1. AND Gate.
2. OR Gate.
3. NOT Gate.
4. NAND Gate.
5. NOR Gate.
6. EX-OR Gate.
7. EX-NOR Gate.

In given above NAND and NOR Logic Gates are called Universal Gates because using these two gates individually any digital circuit can be build.

Truth Table, Graphical Symbol, Algebraic Function of above listed Logic Gates are given below.

• AND Gate
• AND Gate is an electronic circuit which gives a high output only if all its inputs are high, otherwise for all other condition it gives low output. A dot (.) is used for notation of AND operation.

• OR Gate
• OR Gate is an electronic circuit which gives a low output only if all its inputs are low, otherwise it gives a high output for all other combinations of inputs. A plus (+) is used for OR operation.

• NOT Gate
• NOT Gate is an electronic circuit which gives inverted output for each input. That means it gives a high output for low input and low output for high input. 

• NAND Gate
• NAND Gate is an electronic circuit which gives a low output only if all its inputs are high and for other combinations of inputs it gives a high output. NAND Gate is equivalent to AND Gate followed by NOT Gate.

• NOR Gate
• NOR Gate is an electronic circuit which gives a high output only if all its inputs are low and for other combinations of inputs it gives a low output. NOR Gate is equivalent to OR Gate followed by NOT Gate.

• EX-OR Gate
• EX-OR Gate is an electronic circuit which gives a high output only if either, but not both the inputs are high. That means it gives a high output when its both inputs are at different logic levels with respect to each other. An encircled plus (⊕) is used for EX-OR operation.

• EX-NOR 
• EX-NOR is an electronic circuit which gives low output only if either, but not both of its inputs are high.