Physics Investigatory Project On Logic Gates

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CERTIFICATE
This is to certify that <name> of class XII has

satisfactorily completed the project on “LOGIC
GATES” under the guidance of <teachers
name>during the session 2013-2014.
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VALUED BY
TEACHER
EXTERNAL EXAMINER
PRINCIPAL
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DATE:
ACKNOWLEDGME
NT
I'd like to express my greatest gratitude to the

people who have helped & supported me
throughout my project. I’ m grateful to our
school’s PHYSICS faculty
I thank <teachers name> for her continuous support
for the project, from initial advice &
encouragement to this day. Special thanks of
mine goes to my colleagues who helped me in
completing the project by giving
necessary
information on the apparatus used in this
experiment, made this project easy and
accurate.
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I wish to thank my parents for their undivided

support & interest who inspired me &
encouraged me to go my own way without
which I would be unable to complete my
project. At last but not the least I want to
thanks my friends who appreciated me for my
work & motivated
me.
CONTENT
•Introduction
• Experiment
1. Aim 10
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2. Apparatus 10
3. Theory 11
4. Procedure 16
5. Circuits Prepared 22
6. Observations 24
7. Result 26
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Bibliography 27
INTRODUCTION
Logic Gates:
A gate is a digital circuit that follows curtain 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.
(i) NOT gate (Inverter)

This is the most basic gate, with one input and one output.
Produces a ‘1’ output if the input is ‘0’ and vice-versa. That
is, it produces an inverted version of the input at its output.
A Y=A’
0 1
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1 0
(ii) OR Gate
An OR gate has two or more inputs with one output. The

output Y is 1 when either input A or input B or both are 1s,
that is, if any of the input is high, the output is high.
A B Y=A OR B(A+B)
0 0 0
0 1 1
1 0 1
1 1 1
(iii) AND Gate

An AND gate has two or more inputs and one output. The
output Y of AND gate is 1 ,only when input A and input B
are both 1. It kind of looks for the minimum of the two
signals.
A B Y=A AND
B(A.B)
0 0 0
0 1 0
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1 0 0
1 1 1
1
Some Basic Logic Gates and Their Truth
Tables
 Circuit diagrams
 AND GATE
 OR GATE
 NOT GATE
Experiment

AIM
To design and simulate basic
logic gates and to design an
appropriate logic gate
combination for a given truth
table.
APPARATUS
 A project board
 Two N4007 diodes
 Two LED
 A 9v battery with a connector
 Two BPJ-BC547 transistors
 Two 100, three 560 resistors
 Connecting wires
 THEORY
The three basic logic gates and their
combinations are the building block of the
digital circuit.
1. OR +
B
gate B
A
A
The OR gate is an electronic circuit that gives a high

output (1) if one or more of its inputs are high. A plus
(+) is used to show the OR operation.
CIRCUIT DIAGRAM:
2. AND Gate
A A.B
B
The AND gate is an electronic circuit that gives high
output only if all inputs are high
CIRCUIT DIAGRAM :
3.
NOT
Gate
The NOT gate is an electronic circuit that produces an
inverted version of the input at its output. It is also known
as an inverter.
A A’
CIRCUIT DIAGRAM:
0
1
PROCEDURE

 Design of basic logic gates.
DESIGN OF AND GATE


COMPONENTS: Two p-n junction diode, A LED, A

100 resistors
CONSTRUCTION: An AND gate can be realized

by connecting the diodes as shown in the figure. A
resistance of 100 is connected in series with the
LED to prevent its malfunction.
PROJECT BOARD CIRCUIT:
GROUND
HIGH
DESIGN OF OR GATE

COMPONENTS: Two p-n junction diode, A LED, A

100 resistors
CONSTRUCTION: An OR gate can be realized by

connecting the diodes as shown in the figure. Here also
there is a need for a 100 resistor in series with LED

DESIGN OF NOT GATE
COMPONENTS: A transistor, two LEDs, three 560
resistors.
CONSTRUCTION: not gate circuit can be realized by

connecting an NPN transistor as shown in the figure. The
base of the transistor is connected to the input through
resistance of 560 and emitter is connected to the negative
terminal. The collector is connected to the positive
terminal and the output voltage at collector is with respect
to negative.

1
Ground
High line
1=2=3=600
 Logic gate combination for given truth
table
1. Write product term for each input (minterm), Combination
where Boolean function has output
2. While writing minterms, complement the variable whose value

is 0 otherwise write it in the direct form (without complement).
3. Add all the minterms to obtain the Boolean function.
3. Draw the circuit using basic LOGIC Gates.
So we, choose the given Truth Table.

A B Y=A.B Y’
0 0 0 1
0 1 0 1
1 0 0 1
1 1 1 0
The Boolean Function F(x,y) is obtained as:
F(x,y)= X’.Y’+X.Y’+X’Y
= Y’+X’Y <Distributive law>
= (X’+Y’)(Y+Y’) <Distributive law>
= X’+Y’ <law of complements>
= (XY)’ <DeMorgan’s theorem>
So, our expression reduces to that of a NAND Gate

logic (Not of AND).
LOGIC CIRCUIT IS:
F=(x.y)’
x
CIRCUIT DIAGRAM
High line
Ground
 Circuits
Prepared:-
 AND gate
 OR gate
 NOT gate
 NAND gate
OBSERVATION
S

1. Stimulation of AND gate

The following conclusions can be easily drawn from the
working of electrical circuit:
a) If both switches are open (A=0, B=0) then LED will
not glow, hence Y=0.
b) If Switch one switch is open and the other is closed
(A=1, B=0 or A=0, B=1) then LED will not glow, hence
Y=0.
c) If switch A & B both closed (A=1, B=1) then LED wi
ll glow,
Hence Y=1.
2. Stimulation of OR gate
The following conclusions can be easily drawn from the
working of electrical circuit:
a) If both switches are open (A=0, B=0) then LED will
not glow, hence Y=0.
b) If Switch one switch is open and the other is closed
(A=1, B=0 or A=0, B=1) then LED will glow, hence
Y=0.
c) If switch A & B both closed (A=1, B=1) then LED wi
ll glow,
Hence Y=1.
3. Stimulation of NOT gate

a) If switch A is open (i.e. A=0), the LED will glow, hence Y=1.
b) If Switch A is closed (i.e. A=1), the LED will not glow, hence Y=0.
4. Stimulation of NAND gate

a) If Switch A & B open (A=0, B=0) then LED will glow, hence Y=1.
b) If Switch A open B closed then (A=0, B=1) LED will glow, hence Y=1.
c) If switch A closed B open then (A=1, B=0) LED will glow, hence Y=1.
d) If switch A & B are closed then (A=1, B=1) LED will not glow, hence Y=0
Re
sul
t:
Basic logic gates were designed
and simulated and logic circuit
was prepared for the given truth
table
BIBLIOGRAPHY:-
 Wikipedia
 Electronic devices and circuits by J B
Gupta
 Conceptual physics by G C Agarwal
 Encarta

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1|Page

This is to certify that <name> of class XII has

I'd like to express my greatest gratitude to the

I wish to thank my parents for their undivided

Truth tables help understand the behavior of logic gates.

(i) NOT gate (Inverter)

Produces a ‘1’ output if the input is ‘0’ and vice-versa. That

is, it produces an inverted version of the input at its output.

An OR gate has two or more inputs with one output. The

(iii) AND Gate

The OR gate is an electronic circuit that gives a high

 Design of basic logic gates.

DESIGN OF AND GATE

COMPONENTS: Two p-n junction diode, A LED, A

CONSTRUCTION: An AND gate can be realized

PROJECT BOARD CIRCUIT:

COMPONENTS: Two p-n junction diode, A LED, A

CONSTRUCTION: An OR gate can be realized by

PROJECT BOARD CIRCUIT:

CONSTRUCTION: not gate circuit can be realized by

PROJECT BOARD CIRCUIT:

2. While writing minterms, complement the variable whose value

3. Add all the minterms to obtain the Boolean function.

3. Draw the circuit using basic LOGIC Gates.

So we, choose the given Truth Table.

= Y’+X’Y <Distributive law>

= (X’+Y’)(Y+Y’) <Distributive law>

= X’+Y’ <law of complements>

= (XY)’ <DeMorgan’s theorem>

So, our expression reduces to that of a NAND Gate

LOGIC CIRCUIT IS:

1. Stimulation of AND gate

3. Stimulation of NOT gate

4. Stimulation of NAND gate

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