# Logic Gates

Topics: Logic gates, Logic gate, Circuit diagram Pages: 5 (802 words) Published: January 6, 2012
A Project Report On

WORKING OF LOGIC GATES

SUBMITTED BY:-
Shamil Choudhury
ROLL__________ No_____________
Karimganj Junior College Of Science

CONTENTS……..
TOPICS Page No
1. CERTIFICATE1
2. INTRODUCTION 2
3. THEORY3-4
4. EXPERIMENT5-6
5. RESULTS 7
6. CONCLUSION. 7
7. ACKNOWLEDGEMENT 8
8. REFERENCE 9

INTRODUCTION
A gate is a digital circuit that follows certain logical relationship between the input and output voltages. Therefore, they are generally known as logic gates — gates because they control the flow of information. The five common logic gates used are NOT, AND, OR, NAND, NOR. Each logic gate is indicated by a symbol and its function is defined by a truth table that shows all the possible input logic level combinations with their respective output logic levels. Truth tables help understand the behavior of logic gates. These logic gates can be realized using semiconductor devices. Here we will investigate on the working of first three logic gates i.e. OR, AND, and NOT gate.

OBJECTIVE OF THE PROJECT

To demonstrate the working of logic gates using torch bulb, battery and switches.

APPARATUS REQUIRED
To demonstrate the working of the logic gates we require the following apparatus:- i) A BATTERY OF 6 V.
ii) TWO SWITCHES (KEYS).
iii) TORCH BULB.
iv) CONNECTING WIRES

THEORY
There are three basic logic gates:
1. The OR Gate
* An OR gate has two or more inputs with one output. It operates in such a way that a output is high (i.e. 1) if one of the two inputs (or both the inputs) is high. The symbol of OR Gate is
It works on the following truth table:-

2. The AND GATE
* An AND gate has two or more inputs and one output. It operates in such a way that the output is high (i.e. 1) when both the inputs are high. The symbol of AND Gate is

It works on the following truth table:-

3. The NOT Gate
* The NOT gate has single input and single output. The output is not the same as input. If the input is low (i.e. 0), the output is high (i.e. 1). On the other hand, the output will be low (i.e. 0) if the input is high (i.e. 1). In other words it performs a negation operation on the input and called the invertor. The symbol of NOT Gate is

It works on the following truth table:-

PROCEDURE

(1) Working of OR Gate
The electric circuit diagram is as shown

Using the above circuit diagram we proceed as follows:
(i) The switches S1 and S2 are not pluged and the glow of the bulb is recorded (do not glow) .

(ii) Now the switch S1 is plugged (not S2), it is found that the bulb glows.

(iii) Now the switch S2 is plugged (not S1), it is observed that the bulb glows.

(iv) Both the switches are plugged, the bulb glows.

(2) Working of AND gate
The electric circuit diagram is shown

Using the above circuit diagram we proceed as follows:
(i) The switches S1 and S2 are not plugged and the glow of the bulb is recorded (do not glow) .
(ii) Now the switch S1 is plugged (not S2), it is found that the bulb does not glow.
(iii) Now the switch S2 is plugged (not S1), it is observed that the bulb does not glow.
(iv) Both the switches are plugged, the bulb glows.

3. Working of NOT gate
The electric circuit...