A logic gate is just a simple boolean function, which means that it has only either of two outputs. Either 1 or 0, high or low, true or false, whatever you can call it. It is the most elementary tool in building a circuit. A logic gate performs a logical operation on an input and gives the appropriate output for it. Given below are the different logic gates, their symbols, descriptions and truth tables.
This function will have a single input only. It is also called an inverter as it gives the reverse of the input function.
AND GATE:
If ‘0′ is false and ‘1′ is true, then the gate acts as the logical “and” operator. Output will be 1 only if ‘all’ inputs are true. It can have more than 1 input.
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NAND GATE:
It is the NOT AND gate. The inverter bubble reverses the output of the AND gate logic, giving a 0 output only when all inputs are 1.
OR GATE:
If “any one” of the inputs are 1, the output is 1. Output is 0 only if all inputs are 0. It can have more than 1 input.
NOR GATE:
It is the NOT – OR gate. The inverter bubble reverses the output of the OR gate logic giving 1 as the output only if all inputs are 0. It can have more than 1 input.
XOR GATE:
It is the ‘Exclusive – OR’ gate. The output is 1 only when the one of the inputs is 1. And 0 if the inputs are the same.
XNOR GATE:
It is the ‘Exclusive – NOR’ gate is a combination of XOR gate followed by an inverter. The output is 1 only when the both the inputs (even high) are the same and false if the inputs are different.
Universal Logic Gates:
A universal logic gate is one which can implement any Boolean function {0,1}, without the use of any other logic gate. Simply put, a logic gate which can serve the function of ALL other logic gates, including itself.
The NAND and NOR gates are called universal logic gates because all the other gates can be created using these two.
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