Logic Gates

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Computers and digital component use binary 0 and 1, where 0 is low voltage (0 volts) and 1 is high voltage (+5 volts). Binary information is carried by signals and manipulation of binary information is done by logic circuits called as gates.

A circuit whose input and output signals are two states on and off. A gate is logic circuit with one or more input signals but only one output signal.

Basic types of Gates :

AND Gate

• Two or more input signals and one output signal.
• Output is high when both the inputs are high.
• Logic equation Y = A . B called as Boolean equation.
• Where A and B are the inputs and Y is the output for all standard symbols of gates shown below.
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OR Gate

• Two or more input signals and one output signal.
• Output is low when both the inputs are low.
• Logic equation Y = A + B.
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NOT Gate

• One input signal and one output signal, also called as inverter.
• Output is always opposite state of the input.
• Logic equation Y = A
• Where is A is the complement of A.
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NAND (Not AND) Gate

• Two or more input signals and one out signal.
• It has high output when at least one of the input is zero or low.
• All input signals must be high to obtain low output.
• Logic equation Y = A . B
• 

NOR (Not OR) Gate

• One or more input signals and one output signal.
• If one of the input is high then output is low
• Logic equation Y = A + B
• 

XOR (Exclusive OR)Gate

• Two or more input signal and one output signal.
• Output is low when both the inputs are same.
• Logic equation Y = A XOR B
• 

XNOR (Exclusive NOR) Gate

• Two or more input signal and one output signal.
• Is combination of XOR gate followed by invertor.
• Output is high when both the inputs are same.
• Logic equation Y = A XOR B
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