To Construct an Amplifier Using a Transistor

PHYSICS INVESTIGATORY PROJECT TOPIC: TO CONSTRUCT AN AMPLIFIER USING A TRANSISTOR MADE BY: Chinmay Shah CLASS - XII-B GUIDED BY— Mrs. Soma Bandyopadhyay BOARD ROLL NO. —

Chinmay Shah

Physics Investigatory Project

CERTIFICATE This is to certify that Chinmay Shah, student of class XII-B has successfully completed the Physics Project under the guidance of — Mrs. Soma Bandyopadhyay. This project is genuine and is not plagiarism of any kind. The references used in making this project file are declared at the end of the file.

External’s Sign:

Internal’s Sign:

______________

_____________

Principal’s signature School stamp Transistor as Amplifier

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Chinmay Shah

ACKNOWLEDGEMENT I wish to express my deep gratitude and sincere thanks to the Principal, Mrs Murial Fernandez, Ryan International School, Sanpada for her encouragement and for all the facilities she has provided for this project work. I extend my hearty thanks to my subject teacher Mrs. Soma Bandyopadhyay and Lab Assistant Devesh Sir who guided me to the successful completion of this project. I take this opportunity to express my deep sense of gratitude for their invaluable guidance, constant encouragement and 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 classmates who helped me to carry out this project work successfully and for their valuable advice and support which I received for them time to time.

Transistor as Amplifier

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Chinmay Shah


INDEX Sr No.

Contents

Page No.

1

Aim of the Experiment

5

2

Introduction

6

3

Apparatus Required

9

4

Circuit Diagram

10

5

Theory

11

6

Procedure

13

7

Observations

14

8

Graph

16

9

Result

17

10

Conclusion

18

11

Precautions

19

13

Bibliography

20


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Chinmay Shah


AIM To construct amplifier using n-p-n transistor and study its current gain and identify its active region


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Chinmay Shah

INTRODUCTION •

An Amplifier is a device which is used for multiplying the Amplitude of variation of alternating voltage or current or power.

Here’s a diagram of how an amplifier works:

•

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material with three terminals for connection to an external circuit.


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Emitter (E): It is the left hand side thick layer of the transistor which is heavily doped; Base (B): It is a central thin layer of transistor which is lightly doped; Collector (C): It is the right hand side thick layer of the transistor which is moderately doped; A p-n-p junction transistor is obtained by growing a thin layer of thin layer of n-type semi-conductor in between two relatively thick layers of p-type semi-conductor.

A n-p-n junction transistor is obtained by growing a thin layer p-type semiconductor in between two relatively thick layers of n-type semi-conductor.


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Chinmay Shah

In this experiment, we will use a n-p-n transistor.

The common-emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor; the transistor's current amplification combined with the properties of the circuit mean that small swings in V in produce large changes in Vout. Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both. From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved. Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.

APPARATUS REQUIRED


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Chinmay Shah


1. A n-p-n transistor; 2. Two battery eliminators; 3. Two High resistance Rheostats; 4. Connecting Wires; 5. Two One Way keys; 6. Two Ammeters; 7. Two Voltmeters;

CIRCUIT DIAGRAM


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THEORY The circuit details using an n-p-n transistor as a common base amplifier are shown in the circuit diagram •

The base is common to both the input and the output circuits.


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•

•

The input (Emitter Base) circuit is forward biased by using a low voltage battery Vbb. The output (collector base) circuit is reverse biased by using a high voltage battery Vcc.

• Let Ie, Ib and Ic be the emitter current, base current and collector current respectively. Then, according to Kirchhoff’s first law:

Ie = Ib + Ic 

Current Gain (β)=

 Crrn In Crrn

=

 

(ß is defined as AMPLIFICATION and generally has a large value of) •

Voltage gain =

= =β

•

Output Voltage In 

=

 i

Ic.RL IB.Ri  

In the output circuit,

Vcc = Vce - VL Vce = Vcc - VL Transistor as Amplifier

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Vce = Vcc - Ic.RL

(1)

Transition output is Vce •

When Input signal forward biases the (ß - E) section, I c section is large: ICRL > Vcc and Vce is negative from eqn. (1)

When input section is reverse biased, by signal, Ic.RL → 0 So, Vce = Vcc (approx.) c Output is therefore 180˚ out of phase w.r.t input and hence, a second stage of amplification is required.

PROCEDURE • •

Connect the apparatus accordingly as shown in the circuit diagram. Determine the least count and the zero errors of voltmeters and ammeters.


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Keep the potential of the battery V b at a low voltage Make all the connections neat, clean and tight. Note the Least count Increase the voltage from input battery V b from 0 to 0.6 V. Note the input current at this point. Now increase the input current by changing the resistance of rheostat and record the corresponding output current. • Ensure that the input voltage does not exceed 1 V (input and output voltage will change correspondingly). • Plot the readings of the current taken in the graph of Current (inp) vs Current (out). • • • • • •

OBSERVATIONS 

VOLTMETER 1. 2. 3. 4. 5. 6.

Least count of Voltmeter (Vi)= 0.2 V Range of Voltmeter (Vi)= 10 V Zero Error of voltmeter (Vi)= 0 V Least count of Voltmeter (Vo)= 0.2 V Range of Voltmeter (Vo)= 10 V Zero Error of Voltmeter (Vo)= 0 V

AMMETER



1. 2. 3.

Least count of Milliammeter (inp)= 2 mA Range of Milliammeter (inp)= 100 mA Zero error of Milliammeter (inp)= 0 mA


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Chinmay Shah


4. 5. 6.

Least count of Milliammeter (out)= 10 mA Range of Milliammeter (out)= 500 mA Zero error of Milliammeter (out)= 0 mA

OBSERVATION TABLE: Current(Input)(mA) 0.09 0.14 0.25 0.31 0.41 0.47 1.1 1.2 1.3 Transistor as Amplifier

Current(Output)(mA) 1.13 1.36 2.1 2.24 2.9 3.15 11 12.9 13.7 Page 14 of 20

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2.1 2.5 4.2

16.7 19 21.1

Current (inp) vs. Current (out):


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20

15

) t u o ( t n10 e r r u C

5

0 0.09

0.14

0.25

0.31

0.41

0.47

1.1

1.2

1.3

2.1

Current(inp)

RESULT Transistor as Amplifier

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1. As seen from the graph, the active region with maximum current amplification is from 0.41A to 2.0A. 2. Current gain(amplification)(β) =    

= 8.48

3. A minimum of 0.6V needs to be provided as activation voltage to input part of circuit, i.e., base-emitter (BE) section.

CONCLUSION Transistor as Amplifier

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With the experiments carried out in the laboratory to study the characteristics of the NPN transistor proved the aim defined in the report. The NPN transistor has got current amplification in the tune of 8.5 in the region of 0.4 to 2 ma.

PRECAUTIONS •

All the instruments for current and voltage should be of proper range and least count.


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There should be a proper forward and reverse biasing to the transistor input and output section by connecting the batteries with proper polarities. • The readings in voltmeters Vi and Vo should be zero before switching on the batteries. • Never exceed the ratings for the current given in the transistor manual. •

A n-p-n transistor which broke due to the passage of excessive current.

BIBLIOGRAPHY • colorado.edu/physics/phys3330/PDF/Experiment7.pdf Transistor as Amplifier

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Chinmay Shah

• en.wikipedia.org/wiki/Transistor#Transistor_as_an_amplifier • en.wikipedia.org/wiki/Common_emitter • 230nsc1.phy-astr.gsu.edu/hbase/electronic/npnce.html • tedpavlic.com/teaching/osu/ece327/lab1_bjt/lab1_bjt_transistor_ basics.pdf • hyperphysics.phy-astr.gsu.edu/hbase/solids/trans.html

BOOKS•

•

•

Comprehensive Lab manual PHYSICS Class 12; Pradeep Reference Guide for Physics-Class 12; NCERT Physics Part -II Class 12;


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To Construct an Amplifier Using a Transistor

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