1. The document describes an experiment to study the characteristics of a bipolar junction transistor (BJT) operating in common emitter configuration as an amplifier. 2. Key aspects of the experiment include obtaining the input characteristics by varying the base-emitter voltage at constant collector-emitter voltages and measuring the base current, and obtaining the output characteristics by varying the collector voltage at constant base currents and measuring the collector current. 3. The results are presented in tables showing voltages, currents, and calculations to determine characteristics, along with graphs plotting the input and output characteristics. Simulated data and graphs are also provided for comparison with experimental measurements.

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AMERICAN INTERNATIONAL
UNIVERSITY-BANGLADESH
Faculty of Science and Technology
Lab report
Title of the
Experiment:
Study of Transistor Characteristics in Common Emitter Amplifier
Experiment No: 05 Date of Submission: 28 March 2023
Course Title: Electronic Devices Laboratory
Course Code: EEE2104 Section: C .
Semester: Spring 2022-23 Course Teacher: ABRAR FAHIM LIAF
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Group No.: 06
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1 Md Mumtarin Houshain Syam 20-42197-1 BSc [CSE]
Faculty use only
FACULTYCOMMENTS
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Introduction:
A BJT is a three terminal semiconductor device. It is widely used in discrete circuits as well as in
integrated circuits. The main applications of BJTs are analog circuits. For example, BJTs are
used for amplifiers in particular for high speed amplifiers. BJTs can be used for digital circuits as
well, but most of the digital circuits are nowadays realized by field effect transistors (FETs).
There are three operating modes for BJTs, the active mode (amplifying mode), the cut-off mode
and the saturation mode. To apply a BJT as an amplifier, the BJT has to operate in the active
mode. To apply a BJT as a digital circuit element, the BJT has to operate in the cut-off mode and
the saturation mode.
The main objectives of this experiment are to-
1. become familiar with bipolar junction transistors (BJTs)
2. study the biasing of a Common Emitter (CE) Amplifier, and
3. obtain the input and output characteristics of a common-emitter based BJT circuits
Theory and Methodology:
Device structure of bipolar junction transistors
Each BJT consists of two anti-serial connected diodes. The BJT can be either implemented as an NPN or a
PNP transistor. In both cases, the center region forms the base (B) of the transistor, while the external regions
form the collector (C) and the emitter (E) of the transistor. External wire connections to the p and n regions
(transistor terminals) are made through metal (e.g. Aluminum) contacts. A cross section of the two types of
BJTs consisting of an emitter-base junction and a collector base junction is shown in the figure below. An
NPN or a PNP transistors are called bipolar transistors because both types of carriers (electrons and holes)
contribute to the overall current. In the case of a field effect transistor, either the electronics or the holes
determine the current flow. Therefore, a field effect transistor is a unipolar device. The current and voltage
amplification of a BJT is controlled by the geometry of the device (for example width of the base region) and
the doping concentrations in the individual regions of the device. In order to achieve a high current
amplification, the doping concentration in the emitter region is typically higher than that of the base region.
The base is a lightly doped very thin region between the emitter and the collector and it controls the flow of
charge carriers from the emitter to collector region

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Circuit Configuration:
The following figures show the symbol for the npn transistor and pnp transistor. The emitter
of the BJT is always marked by an arrow, which indicates whether the transistor is an npn or a
pnp transistor.
npn BJT symbol pnp BJT symbol
There are three basic ways in which a BJT can be configured. In each case, one terminal is
common to both the input and output circuit shown in figure above.
1. The common emitter configuration is used for voltage and current amplification and is
the most common configuration for transistor amplifiers.
2. The common collector configuration often called an emitter follower, since its output
is taken from the emitter resistor. It is useful as an impedance matching device since its
input impedance is much higher than its output impedance.
3. The common base configuration is used for high frequency applications because the
base separates the input and output, minimizing oscillations at high frequency. It has a
high voltage gain, relatively low input impedance and high output impedance compared
to the common collector.
Biasing of Bipolar Junction Transistors:
In most of the cases, the BJT is used as an amplifier or switch. In order to perform these
functions, the transistor must be correctly biased. Depending on the bias condition (forward or
reverse) of each of the BJT junctions, different modes of operation of the BJT are obtained.
The three mode are defined as follows:
1. Active: Emitter junction is forward biased, collector junction is reverse biased. The BJT
operates in the active mode and the BJT can be used as an amplifier.
2. Saturation: Both the emitter and collector junctions are forward biased. If the BJT is
used as a switch, the saturation mode corresponds to the on state of the BJT.
3. Cut-off: Both the emitter and collector junction are reverse biased. If the BJT is used as a
switch, the cut-off mode corresponds to the off state of the BJT.

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Input and Output Characteristics:
The input characteristics curves are plotted between IB and VBE keeping the voltage, VCE,
constant. The input characteristics look like the characteristics of a forward-biased diode. The
base-to-emitter voltage varies only slightly. The input dynamic resistance is calculated from
the ratio of the small change of base-to-emitter voltage to the small change of base current.
Fig: BJT Common Emitter Input Characteristics
The output characteristics curves are plotted between the collector current, IC, and the collector-
to-emitter voltage drop by keeping the base current, IB, constant. These curves are almost
horizontal. The output dynamic resistance again can be calculated from the ratio of the small
change of emitter-to-collector voltage drop to the small change of the collector current.
Fig: BJT Common Emitter Output Characteristics
Apparatus:
• Trainer Board
• Transistor : C828 (1pc)
• Resistors : 1 KΩ (1pc)& 10KΩ (1pc)
• Multimeter
• DC Power Supply
• Power Supply Cable : (2pc)

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Precautions:
Transistors are sensitive to be damaged by electrical overloads, heat, humidity, and radiation.
Damage of this nature often occurs by applying the incorrect polarity voltage to the collector
circuit or excessive voltage to the input circuit. One of the most frequent causes of damage to
a transistor is the electrostatic discharge from the human body when the device is handled. The
applied voltage, current should not exceed the maximum rating of the given transistor.
Experimental Procedure:
Circuit Diagram:
1. The terminals of the transistor were identified.
2. The circuit connections were made as shown in the above figure.
3. For input characteristics, the voltage 𝑉𝐶𝐸 were fixed and the voltage 𝑉𝐵𝐵 were varied and
the Base current 𝐼𝐵 were calculated using 𝐼𝐵 =
𝑉𝐵𝐵−𝑉𝐵𝐸
10.02𝐾
4. For output characteristics, the input circuit were opened at first (i. e. to make IB = 0). The
collector voltage 𝑉𝐶𝐶 were varied in steps of 4V and the Collector current 𝐼𝐶 were calculated
using 𝐼𝐶 =
𝑉𝐶𝐶−𝑉𝐶𝐸
984
5. Now the input circuit was closed and the base current 𝐼𝐵 was fixed at 50μA by varying 𝑉𝐵𝐵. The
voltage 𝑉𝐶𝐶 were varied according to the table and 𝐼𝐶 were calculated in each step. The process
was repeated for other values of 𝐼𝐵.
6. The input and output characteristic graphs were plotted.
Data Table:
1. Input Characteristics
VCC = 8V VCC = 16V
VBB VBE IB VBB VBE IB
0v 0.0211v 0.21 µA 0v 0.025v 0.25 µA
0.5v 0.51v 0.998 µA 0.5v 0.52v 0.9 µA
1v 0.72v 27.94 µA 1v 0.724v 27.5 µA
1.5v 0.734v 76.85 µA 1.5v 0.743v 75.5 µA
2v 0.75v 124.75 µA 2v 0.761v 123.65 µA
2.5v 0.767v 172.1 µA 2.5v 0.781v 171.56A

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2.Output Characteristics
IB = 0μA IB = 50μA IB = 100μA
VCC VCE IC VCC VCE IC VCC VCE IC
0v
0v 0
0v
0.02v 0.02 mA
0v
0.0169v 0.017 mA
4v
4v 0
4v
0.407v 3.65 mA
4v
0.129v 3.9 mA
8v
8v 0
8v
4.1v 3.96 mA
8v
0.45v 7.66 mA
12v
12v 0
12v
7.93v 4.13 mA
12v
3.341v 8.79 mA
16v
16v 0
16v
11.79v 4.27 mA
16v
6.85v 9.29 mA
Simulation and Measurement:
The following Figure are for:Transistor Characteristics diagram
.

7. 7 | P a g e
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
I
B
(𝝁𝑨)
VBE (V)
IB vs VBE
0
2
4
6
8
10
-2 0 2 4 6 8 10 12 14 16 18
𝐼_𝐶
𝑉_𝐶𝐸
𝐼_𝐶 𝑣𝑠 𝑉_𝐶𝐸
IB 50uA
IB 100uA
IB 0uA
-20
0
20
40
60
80
100
120
140
0 1 2 3 4 5 6 7 8 9 10
𝐼_𝐵
𝐼_𝐶
𝐼_𝐵 𝑣𝑠 𝐼_𝐶
Graph :

8. 8 | P a g e
Simulation Table And Graphs:
1. Input Characteristics
VCC = 8V VCC = 16V
VBB VBE IB VBB VBE IB
0v 0.0000001v 0.000011µA 0v 0.0000002v 0.000021µA
0.5v
0.4996v 0.035µA
0.5v
0.4996vv 0.0355µA
1v 0.7065vv 29.295µA 1v 0.7065v 29.295µA
1.5v 0.723v 77.54µA 1.5v 0.735v 76.344µA
2v 0.724v 127.351µA 2v 0.744v 125.324µA
2.5v 0.725v 177.168µA 2.5v 0.745v 175.152µA
2. Output Characteristics
IB = 0μA IB = 50μA IB = 100μA
VCC VCE IC VCC VCE IC VCC VCE IC
0v
0v 0
0v
0.0166v 0.0168mA
0v
0.019v 0.0195mA
4v
4v 0.000004mA
4v
0.145v 3.918mA
4v
0.117v 3.946mA
8v
8v 0.000008mA
8v
0.272v 7.854mA
8v
0.151v 7.977mA
12v
12v 0.000012mA
12v
3.827v 8.305mA
12v
0.185v 12.007mA
16v
16v 0.000016mA
16v
7.444v 8.695mA
16v
0.528v 15.724mA
-20
0
20
40
60
80
100
120
140
160
180
200
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
IB vs VBE

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Calculations:
𝐼𝐵 =
𝑉𝐵𝐵−𝑉𝐵𝐸
10.02𝐾
For Vcc=8V,
𝐼𝐵 =
0−0.0211
10.02𝑘
= 0.21µA
𝐼𝐵 =
0.5−0.51
10.02𝑘
= 0.998µA
𝐼𝐵 =
1−0.72
10.02𝑘
= 27.94µA
𝐼𝐵 =
1.5−0.734
10.02𝑘
= 76.85µA
𝐼𝐵 =
2−0.75
10.02𝑘
= 124.75µA
𝐼𝐵 =
2.5−0.767
10.02𝑘
= 172.1µA
For Vcc=16V,
𝐼𝐵 =
0−0.025
10.02𝑘
= 0.25µA
𝐼𝐵 =
0.5−0.52
10.02𝑘
= 0.9µA
𝐼𝐵 =
1−0.724
10.02𝑘
= 27.5µA
𝐼𝐵 =
1.5−0.743
10.02𝑘
= 75.5µA
𝐼𝐵 =
2−0.761
10.02𝑘
= 123.65µA
𝐼𝐵 =
2.5−0.781
10.02𝑘
= 171.56µA
𝐼𝐶 =
𝑉𝐶𝐶−𝑉𝐶𝐸
984
For 𝐼𝐵 = 50µA,
𝐼𝐶 =
0−0.02
984
= 0.02𝑚𝐴
𝐼𝐶 =
4−0.407
984
= 3.65𝑚𝐴
𝐼𝐶 =
8−4.1
984
= 3.96𝑚𝐴
𝐼𝐶 =
12−7.93
984
= 4.13𝑚𝐴
𝐼𝐶 =
16−11.79
984
= 4.27𝑚𝐴
For 𝐼𝐵 = 100µA,
𝐼𝐶 =
0−0.0169
984
= 0.017𝑚𝐴
𝐼𝐶 =
4−0.129
984
= 3.9𝑚𝐴
𝐼𝐶 =
8−0.45
984
= 7.66𝑚𝐴
𝐼𝐶 =
12−3.341
984
= 8.79𝑚𝐴
𝐼𝐶 =
16−6.85
984
= 9.29𝑚𝐴
0
2
4
6
8
10
12
14
16
18
-2 0 2 4 6 8 10 12 14 16 18
IC vs VCE

10. 10 | P a g e
Input and output characteristics in terms of the three regions of operation: Cutoff, Active, Saturation:
The input characteristics curves are plotted between IB and VBE keeping the voltage, VCE,
constant. The input characteristics look like the characteristics of a forward-biased diode. The
base-to-emitter voltage varies only slightly. The input dynamic resistance is calculated from
the ratio of the small change of base-to-emitter voltage to the small change of base current.
Fig: BJT Common Emitter Input Characteristics
The output characteristics curves are plotted between the collector current, IC, and the collector-
to-emitter voltage drop by keeping the base current, IB, constant. These curves are almost
horizontal. The output dynamic resistance again can be calculated from the ratio of the small
change of emitter-to-collector voltage drop to the small change of the collector current.
Fig: BJT Common Emitter Output Characteristics
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
I
B
(𝝁𝑨)
VBE (V)
IB vs VBE
0
1
2
3
4
5
6
7
8
9
10
-2 0 2 4 6 8 10 12 14 16 18
𝐼_𝐶
𝑉_𝐶𝐸
𝐼_𝐶 𝑣𝑠 𝑉_𝐶𝐸
IB 50uA
IB 100uA
IB 0uA

11. 11 | P a g e
Q-point and its significance:
The point where the load line and the characteristic curve intersect is the Q-point, which identifies
ID and VD for a particular diode in a given circuit. the Q Point is the relationship between the diode
forward voltage and current defined by the device characteristic. Consequently, there is only one
point on the dc load line where the diode voltage and current are compatible with the circuit
conditions. this operating point (Q point) is the intersection where the optimum forward voltage and
forward current converge, and it is also the point where the diode operates at its optimum.
The Q point is essential to the overall component and circuit functionality. It ensures that non-linear
components like diodes operate at their optimal current and voltage throughout the operating range.
This also promotes increased functionality, reliability, and life cycle of your electronic circuits
Discussion & Conclusion:In this experiment, the basic concept of Transistor Characteristics in
Common Emitter Amplifier has observed and a basic circuit using transistor have been
constructed. Research methods have been developed, investigated, and described by measuring,
calculating, and determining the characteristic curve of a transistor. Also, biasing of bipolar
junction transistor such as active, saturated, and cutoff has been observed. The transistor, resistor
and the multimeter were checked before the start of the experiment.
The value of resistors was measured using multimeter carefully.
Reference(s):
1. Adel S. Sedra, Kennth C. Smith, Microelectronic Circuits, Saunders College
Publishing, 3rd ed., ISBN: 0-03-051648-X, 1991.
2. American International University–Bangladesh (AIUB) Electronic Devices Lab
Manual.
3. David J. Comer, Donald T. Comer, Fundamentals of Electronic Circuit Design,
john Wiley & Sons Canada, Ltd.; ISBN: 0471410160, 2002.