2017-2018
PHYSICS INVESTIGATORY PROJECT
L OG O G I C G A TE TE S Supervised by: -
Submitted by:-
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It is certified that the project work entitled “LOGIC GATES” as a record of investigatory work done by the student ABHIJEET BISHNOI during the academic year 2017-18 under my guidance and supervision in practical fulfillment of the requirement for the “All India Senior School Certificate Examination” conducted by CBSE.
PGT, Physics
Signature
Signature
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I wish to express my deep gratitude and sincere thanks to the Principal, Dr. Tabassum Khan for her encouragement and for all the facilities that she provided for this project work. I extend my hearty thanks to Mr. Ajay Gehlot, our Physics Teacher, who guided me to the successful completion of this project. I take this opportunity to express my deep sense of gratitude for his invaluable guidance, constant encouragement, immense motivation, which has sustained my efforts at all stages of this Project work. I can’t forget to offer my sincere thanks to my parents and also to my classmates who helped me to carry out this project work successful and for their valuable advice and support, which I received from them time to time .
AB H I J E E T BI SH NOI
Class: - XII – A Army Public School, Jodhpur 4
A logic gate can be defined as digital circuit which either allows a signal to pass through or stops it. These gates are related to Boolean Algebra. These gates allow signals to pass through them only when some logic is satisfied. A semiconductor diode {P — N junction) acts as a closed switch when it is forward biased, i.e. it allows current to pass through it. It acts as an open circuit when it is reversed biased, i.e. it allows very little or no current to pass through it. This unique property of diode is employed in the design of logic gates and the circuits.
The logic gates are building blocks of electronic devices. Logic gate may have one or more inputs but can only have one output. Possible values of input and output of logic gates are expressed in form of tables called truth tables.
Two values of logic statement are denoted by binary numbers 1 and 0 where 1 represent higher value.
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Any Boolean algebra operation can be associated with inputs and outputs represent the statements of Boolean algebra. Although these circuits may be complex, they may all be Constructed from three basic devices. We have three different types of logic gates .These are the AND gate, the OR gate and the NOT gate.
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0
HIGH
LOW
+ve
-ve
ON
OFF
CLOSE
OPEN
RIGHT
WRONG
TRUE
FALSE
YES
NO
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Information converted in electrical form and suitable for transmission called a signal. There are two types of signals
Analogue signals are continuous variation of voltage or current. They are essentially single-valued function of time. Sine wave is a fundamental analogue signal
Digital signal are those which can take only discrete step wise value. Binary system that is extensively used in digital electronics employs just two levels of signals. “0” corresponds to low level and “1” corresponds to high level of voltage or current.
The electrical circuit which uses only digital signals is called digital circuit.
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It is a device that combines A with B to give Y as the result. The OR gate has two or more inputs and one output. The logic gate of OR gate with A and B input and Y output is shown below:
In Boolean algebra, addition symbol (+) is referred as the OR. The Boolean expression: A+B=Y, indicates Y equals A OR B. 2.
It 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:
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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.
3. It is a device that inverts the inputs. The NOT is a one input and one output. The logic gate of NOT gate with A and Y output is shown below:
In Boolean algebra, bar symbol (_) is referred as the NOT. The Boolean expression: X’ =Y, indicates Y equals NOT X
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Aim: TO DESIGN AND SIMULATE THE OR GATE CIRCUIT.
Components: Two ideal p-n junction diode (D1 and D2).
Theory and Construction: An OR gate can be realize by the electronic circuit, making use of two diodes D1 and D2 as shown in the figure. Here the negative terminal of the battery is grounded and corresponds to the 0 level, and the positive terminal of the battery (i.e. voltage 5V in the present case) corresponds to level 1. The output Y is voltage at C w.r.t. earth.
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1. 2. 3. 4.
If switch A & B are open LED do not glow (A=0, B=0), Hence Y=0. If Switch A open B closed then LED glow (A=0, B=1), Hence Y=1. If switch A closed B open then LED glow (A=1, B=0), Hence Y=1. If switch A & B are closed then LED glow (A=1, B=1) , Hence Y=1.
A
B
Y
0
0
0
0
1
1
1
0
1
1
1
1
Aim: TO DESIGN AND SIMULATE THE AND GATE CIRCUIT.
Components: Two ideal p-n junction diode (D1 and D2), a resistance R.
Theory and Construction: An AND gate can be realize by the electronic circuit, making use of two diodes D1 and D2 as shown in the figure. The resistance R is connected to the positive terminal of a 5V battery permanently. 11
Here the negative terminal of the battery is grounded and corresponds to the 0 level, and the positive terminal of the battery (i.e. voltage 5V in the present case) corresponds to level 1. The output Y is voltage at C w.r.t. earth.
1. If both switches A&B are open (A=0, B=0) then LED will not glow, Hence Y=0. 2. If Switch A closed & B open (A=1, B=0) then LED will not glow, Hence Y=0. 3. If switch A open & B closed (A=0, B=1) then LED will not glow, Hence Y=0. 4. If switch A & B both closed (A=1, B=1) then LED will glow, Hence Y=1.
A
B
Y
0 1 0 1
0 0 1 1
0 0 0 1 12
Aim: TO DESIGN AND SIMULATE THE NOT GATE CIRCUIT.
Components: An ideal n-p-n transistor.
Theory and Construction: A NOT gate cannot be realized by using diodes. However an electronic circuit of NOT gate can be realized by making use of a n-p-n transistor as shown in the figure. The base B of the transistor is connected to the input A through a resistance Rb and the emitter E is earthed. The collector is connected to 5V battery. The output Y is voltage at C w.r.t. earth.
1. If switch A is open (i.e. A=0), the LED will glow, Hence Y=1. 2. If Switch A is closed (i.e. A=1), the LED will not glow, Hence Y=0.
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A
Y
0
1
1
0
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‘
’
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REFERENCES
TAKEN FROM NCERT AND PRADEEP
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