Logic Gates:
Logic gates are the basic building blocks of the digital circuits. These logic gate circuits are made up of diodes, transistors and resistors.
Most of the electronic devices which we use everyday like our smart phones, tablet, laptops and memory devices use logic gates in their electronic circuits.
Logic gates have two or more inputs and one output. The inputs and outputs are either ‘0’ or ‘1’. The logic gates take decisions the output.
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| Types of Logic Gates |
These are the types of Logic Gates. Let us discuss about each Logic Gate in detail.
AND:
AND Logic Gate produces the output ‘1’ only when all the inputs are ‘1’. AND operation is denoted by ‘*’. This Logic Gate operation is similar to ordinary multiplication.
Two input AND gate and its truth table:
Y= A*B
Three input AND gate and its truth table:
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| Three input AND gate's truth table |
OR:
OR operation is similar to ordinary addition but it is not exactly equal to addition. It is represented by ‘+’. The OR logic gates produces the output ‘1’ when any one of the input is ‘1’. It produces the output ‘0’ when all the input is ‘0’.
Two input OR gate and its truth table:
Y=A+B
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| Two input OR gate |
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Two input OR gate's truth table
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Three input OR gate and its truth table:
Y=A+B+C
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| Three input OR gate |
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| Three input OR gate's truth table |
NOT:
NOT gate has only one input and one output. It is also called as inverter or complementation. It is denoted by (').
Y=A'
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| NOT Gate |
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| NOT Gate truth table |
NAND:
NAND gate operation is inversion operation of AND gate. So the output of the AND gate is complimented. It produces the output ‘0’ when all the inputs are ‘1’. It produces ‘0’ for all other combinations of input.
Two input NAND gate and its truth table:
Y=(A*B)'
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Two input NAND Gate
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| Two input NAND Gate's truth table |
Three input NAND gate and its truth table:
Y=(A*B*C)'
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| Three input NAND Gate |
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| Three input NAND Gate's truth table |
NOR:
NOR gate operation is inversion operation of OR gate. So the output of the OR gate is complimented. It produces the output ‘1’ when all the inputs are ‘0’. It produces ‘0’ for all other combinations of input.
Y=(A+B)'
Two input NOR gate and its truth table:
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| Two input NOR gate |
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| Two input NOR Gate's truth table |
Three input NOR gate and its truth table:
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| Three input NOR Gate |
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| Three input NOR Gate's truth table |
Exclusive–OR (XOR):
XOR operation is denoted by encircled plus sign . The output is ‘1’ when either of the input is high. When both the inputs are same, that is when both are ‘1’ or ‘0’, it produces ‘0’ output.
Two input Ex-OR gate and its truth table:
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| Ex-OR Gate |
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| Two input Ex-OR Gate truth table |
Three input Ex-OR gate and its truth table:
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| Three input Ex-OR Gate |
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| Three input Ex-OR Gate truth table |
Exclusive–NOR:
Ex-NOR is the compliment gate of XOR. It produces the output ‘1’ when both the inputs are same, that is when both are ‘1’ or ‘0’. It produces the output ‘0’ when either of the input is ‘1’.
Two input Ex-NOR gate and its truth table:
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| Two input Ex-NOR Gate |
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| Two input Ex-NOR Gate's truth table |
Three input Ex-NOR gate and its truth table:
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| Three input Ex-NOR gate and its truth table |
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