AND, OR and NOT are three basic operations in Boolean algebra; and AND, OR and NOT gates are three basic gates in digital electronics. Actually all logic gates are made of these three gates.
Definition of NAND operation
NAND operation is a Boolean operation where output is false only if all operands are true.
In terms of NAND gate
NAND gate circuit is a logic circuit where output is always one except when all inputs are one.
There is an important point to note in the truth table above. At first we may consider AND operation on two operands (inputs) A and B, after that we are inverting the result with NOT operation. This is how NAND gate works.
NAND gate in simple words
NAND gate is like connecting an AND gate output to a NOT gate input like the figure below:
NAND gate may have three or more inputs
Boolean expression for NAND gate operation which is read as x = not A.B,
NAND and NOR gates are called universal gate because you can construct any gate using NAND gate or NOR gate.
In the circuit diagram above you will notice that output is always high except when both transistors are biased. It’s possible only when both inputs are high.
NAND gate IC
Various NAND gate ICs are available in market, 7400 is one of them. It’s a 14 pin two input NAND gate IC where four NAND gates are packed. It works on 5 volt power supply.