Some Logical Moments With Logic Gates

Sorry for this long break as I was away, could not post the required notes as schedule d, today we will go through basic logic gates. Logic Gates: A logic gate is an elementary digital circuit. Logic gates process signals which represent true or false. Normally the positive supply voltage +Vs represents true or high and 0V represents false or low. Truth Table: Truth tables are used to help show the function of a logic gate. Number of terms depend upon the number of Input. It will be always 2ⁿ,where 'N' is the numbers of Inputs. AND gate The AND gate is an electronic circuit that gives a high output(1) if all its inputs are high. A dot (.) is used to show the AND operation i.e. A.B.
Truth Table			AND Gate
A	B	A.B
0	0	0
0	1	0
1	0	0
1	1	1

OR Gate The output is true if one of input is true or both of them are true. An OR gate can have two or more inputs.
Truth Table			OR Gate
A	B	A+B
0	0	0
0	1	1
1	0	1
1	1	1

NOT gate (inverter) The output is true when the input A is NOT true, the output is the inverse of the input. A NOT gate can only have one input. A NOT gate is also called an inverter.
Truth Table			NOT Gate
	A	Ā
	0	1
	1	0

NAND Gate: The NAND gate operates as an AND with NOT gate to follow. It acts in the manner of the logical operation AND followed by negation. The output is false if both inputs are true. Otherwise, the output is true.
Truth Table			NAND Gate
A	B	(A.B)'
0	0	1
0	1	1
1	0	1
1	1	0

NOR Gate: The NOR gate operates as an OR with NOT gate to follow. It acts in the manner of the logical operation Or followed by negation. The output is true if both inputs are false, otherwise, the output is false.
Truth Table			NOR Gate
A	B	(A+B)'
0	0	0
0	1	0
1	0	0
1	1	1

XOR Gate: The 'Exclusive-OR' gate is a circuit which will give a high output if either, but no t both, of its two inputs are high. While writing the truth table using more than three input remember when numbers of 1 is odd in input values then output will be 1. An encircled plus sign Å is used to show the XOR operation. The Boolean Expression : A'B + B'A
Truth Table			XOR Gate
A	B	A'B + B'A
0	0	0
0	1	1
1	0	1
1	1	0

		Diagram Using Logic Gates



XNOR Gate: The XNOR [Exclusive-NOR] gate is a XOR gate followed by an inverter. Its output is true if the inputs are the same, and false if the inputs are different. The Boolean Expression : (A'B + B'A)'

Truth Table			XNOR Gate
A	B	(A'B + B'A)'
0	0	1
0	1	0
1	0	0
1	1	1