Submitted by:- Lakhvinder Singh

INVESTAGOTARYPROJECT PHYSICS

__________2015-2016

Submitted to:- A.K. Singh

KENDRIYA VIDYALAYA No .2AFS STATION,MAHARAJAPURA,GWALIOR

Logic gates

INDEX 1)  INTRODUCTION2) LOGIC (BASIC) GATES3) THE OR GATE4) THE AND GATE5) THE NOR GATE6) THE NAND GATE7) BIBLIOGRAPHY  

This is to certify that Lakhvinder Singh of class XII has satisfactorily completed the.Project on “LOGIC GATES” under the guidance of Mr. A.K. Singh during the session 2015-2016 towards partial fulfillment of credit for the Physics practical evaluation of CBSE 2015, and Submitted satisfactory report, as compiled in the following pages, under my supervision.

MISS.REKHA SAXENA MR.A.K SINGH(PRINCIPLE ) (PGT PHYSICS)

CERTIFICATE

The successful completion of any task would be incomplete without mentioning the names of those persons who helped to make it possible. I take this opportunity to express

my gratitude in few words and respect to all those who helped me in the completion of this project.

It is my humble pleasure to acknowledge my deep senses of gratitude to my Physics teacher, Teacher name for her valuable support, constant help and guidance at each and every stage,

without which this project would not have come forth.

I also register my sense of gratitude to our principal, Mr.principal, for his immense encouragement that has made this project successful.

I would also like to thank my friends and family for encouraging me during the course of this project.

Last, but not the least, I would like to thank CBSE for giving us the opportunity to undertake this project.

ACKNOWLEDGEMENT

LOGIC GATE• Actually the term logic is applied to digital circuits used to implement

logic functions. Several kinds of digital logic circuits are the basic elements that form the building blocks for such complex digital system as the computer.

• The lines connected to each symbols are the inputs and outputs. • The inputs are on the left of each symbol and the output is on the right.

• A circuit that performs a specific logic operation (AND, OR) is called a logic gate.

INTRODUCTIONA gate is defined as a digital circuit which follows some logical relationship between the input and output voltages.  It is a digital circuit which either allows a signal to pass through as stop, it is called a gate.The logic gates are building blocks at digital electronics.  They are used in digital electronics to change on voltage level (input voltage) into another (output voltage) according to some logical statement relating them.A logic gate may have one or more inputs, but it has only one output.  The relationship between the possible values of input and output voltage is expressed in the form of a table called truth table or table of combinations

Truth table of a Logic Gates is a table that shows all the input and output possibilities for the logic gate.George Boole in 1980 invented a different kind of algebra based on binary nature at the logic, this algebra of logic called BOOLEAN ALGEBRA.   A logical statement can have only two values, such as HIGH/LOW, ON/OFF, CLOSED/OPEN, YES/NO, RIGHT/WRONG,TRUE/FALSE,CONDUCTING/NON-CONDUCTING etc.  The two values of logic statements one denoted by the binary number 1 and 0.  The binary number 1 is used to denote the high value.  The logical statements that logic gates follow are called Boolean expressions. 

THE AND GATE• An AND gate can have two or more inputs and performs what is know as

multiplication. • The output of AND gate is high when all inputs are high otherwise all outputs are

low.THE AND GATE is a device that combines A with B to give Y as the result. The AND gate has two or more inputs and one output. The logic gate of AND gate with A and B input and Y output is shown below: In Boolean algebra, multiplication sign (either x or.) is referred as the AND

The Boolean expression:  A.B=Y, indicates Y equals A AND B.

OPERATION OF AND GATE• An AND gate produces a HIGH output only when all of the inputs are HIGH. When

any of the inputs is LOW, the output is LOW. Therefore, the basic purpose of AND gate is to determine when certain conditions are simultaneously true, as indicated by High levels on all of its inputs, and produces a High on its output.

Inputs OutputA B X0 0 00 1 01 0 01 1 1

Logical Symbol Truth Table

THE OR GATE• OR gate can have two or more inputs and performs what is known as

logical addition. • The output of OR gate is Low when all inputs are low, otherwise all

outputs are high The following interference can be easily drawn from the working of

electrical circuit is: a)         If switch A & B are open lamp do not glow (A=0, B=0),

hence Y=0. b)         If Switch A open B closed then (A=0, B=1) Lamp glow,

hence Y=1. c)         If switch A closed B open then (A=1, B=0) Lamp glow,

hence Y=1. d)         If switch A & B are closed then (A=1, B=1) Lamp glow,

hence Y=1.

OPERATION OF AN OR GATE • An OR gate produces a High on the output when any of the inputs is High.

The output is Low only when all of the inputs are Low. Therefore, an OR gate determines when one or more of its inputs are High and produces a High on its output.

Logical SymbolInputs Output

A B X0 0 00 1 11 0 11 1 1

Truth Table

THE NAND GATE• The NAND gate is the one of the popular logic element because it can be

used as a universal gate; that is NAND gate can be used in combination to perform the AND, OR, and inverter operations.

• NAND Gate is constructed by attaching NOT Gate at the output of AND Gate, hence NAND Gate is called NOT- AND Gate.

• NAND Gate has two or more input and only one output. • The output of NAND gate is low when all inputs are high, otherwise all

outputs are high.

OPERATION OF A NAND GATE• A NAND gate produces a Low output only when all the inputs are High.

When any of the inputs is Low, the output will be High.

Logical SymbolInputs Output

A B X0 0 10 1 11 0 11 1 0

Truth Table

THE NOR GATE• The NOR gate, like the NAND gate, NOR gate is also useful logical

element because it can also be used as a universal gate. • NOR gate can be used in combination to perform the AND, OR and

Inverter operations. • NOR Gate is the combination of NOT gate at the output of OR gate, hence

NOR gate is type of NOT-OR gate. • NOR gate has two or more input and only one output. • The Output of NOR gate is high when all inputs are low otherwise the

output is low.

OPERATION OF NOR GATE• A NOR gate produces a Low output when any of its inputs is high. Only

when all of it’s inputs are low is the output high.

Logical SymbolInputs Output

A B X0 0 10 1 01 0 01 1 0

Truth Table

BIBLOGRAPHYEncarta Encyclopaedia. Britannica Encyclopaedia.www.wikipedia.com.www.answers.com.www.google.co.in. NCERT TEXTBOOK PHYSICS