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Date Performed:

ACTIVITY 10

COMMON EMITTER FIXED BIAS AMPLIFIER CONFIGURATION

INTRODUCTION:

The common emitter transistor amplifier circuit is one of the mainstay circuits for use within electronic design.
The common emitter circuit configuration is used as a basic switch for logic circuits, as an analogue amplifier
and in many other applications.

The common emitter circuit configuration provides voltage gain combined with a moderate current gain, as well
as a medium input and a medium output impedance. As such the common emitter configuration is a good
allround circuit for use in many applications.

It is also worth noting at this stage that the common emitter transistor amplifier inverts the signal at the input.
Therefore, if a waveform that is rising enters the input of the common emitter amplifier, it will cause the output
voltage to fall. In other words, it has a 180° phase change across the circuit.

The common emitter amplifier has the signal applied to the base and the output is then taken from the collector
circuit. As the name of this circuit implies, the emitter circuit is common to both input and output.

OBJECTIVES:
  Discuss the operation of Common Emitter Fixed Bias configuration using Bipolar Junction Transistor.
INSTRUMENTS AND COMPONENTS:

 1 Audio Generator / Function Generator

 Variable DC Supply (0 – 30 Vdc)
 Multimeter
 2 – 2N4123 or equivalent BJT
Transistors
 2 – 390 kΩ ¼ watts

DIAGRAMS:

 2 – 2.2 kΩ ¼ watts
 2 – 1 microFarad / 25 V Electrolytic
capacitor
 Connecting wires
 Breadboard
 Figure 10.1

PROCEDURES:

1. Implement Figure 10.1 on the breadboard.

2. Using the Multimeter, measure VB, VC, VE, VCE, IB, IC, IE. Record the results in Table 10.1.
3. From the actual value of β = IC/IB, determine the value of Zi, Zo, AV, and output Voltage AC using the
measured value of input VI from the audio generator. Record the results in Table 10.1.

4. Compute the VB, VC, VE, VCE, IB, IC, IE, Zi, Zo, AV, and output voltage AC and record the results in Table
10.1.
OBTAINED RESULTS:
Table 10.1

Quantities Measured Values Computed Values

Voltage at the Base 700.411mV 19.3V
Voltage at the Collector 172.121mV 20V
Voltage at the Emitter 0V 0V
Voltage at Collector-Emitter 8mV
Current at the Base 48.441µA 49.49
µA
Current at the Collector 3.992mA 3.57m
A
Current at the Emitter 3.31mA 3.61m
A

Input Impedance 0.5Ω

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 Output Impedance 5.6k Ω
Voltage Gain
Voltage Output AC 5.03V

COMPUTATIONS:

Vcc-VBE/RB = IB Ic = β IB = β(Vcc-VBE)/RB *KVL Ic= Vcc/ RC β= Ic/ IB

20-0.7/390k=49.49 µA Ic = β(49.49µA) = 3.57mA 20/5.6k=3.57mA 3.57mA/49.49µA = 72

VcE = Vcc- (IcRc) VE = 0V IE= (β+1) IB

20v-(3.57mA)(5.6k) =8mV (73)(49.49µA) =3.61mA

VcE=Vc-VE RE=25mV/IE *Zo= RC

VBE=VB-VE RE=25mV/3.61mA = 6.93Ω Zo=5.6KΩ

*VE= 0V *Zin= β(RE)

VcE=Vc Zin=72(6.93Ω) =498.96Ω
VBE=VB
 QUESTIONS:
1. What have you notice to collector voltage if the collector resistor is shorted?
-Based on our Experiment the measured on the collector voltage is going up or to be precise to say it has
been saturated.

2. What happen to the voltage gain based on question 1?

-The Voltage gain AC is in more than 1kV which is was increased on its voltage gain based on the
normal circuit and too much Saturated.

CONCLUSION:

Therefore, I conclude that base on our experiment in COMMON EMITTER FIXED BIAS AMPLIFIER
CONFIGURATION we learn that it is the commonly used circuit .
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ACTIVITY 11

COMMON EMITTER VOLTAGE DIVIDER AMPLIFIER CONFIGURATION

INTRODUCTION:
The below circuit diagram shows the working of the common emitter amplifier circuit and it consists of voltage
divider biasing, used to supply the base bias voltage as per the necessity. The voltage divider biasing has a
potential divider with two resistors are connected in a way that the midpoint is used for supplying base bias

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voltage
.

There are different types of electronic components in the common emitter amplifier which are R1 resistor is
used for the forward bias, the R2 resistor is used for the development of bias, the RL resistor is used at the
output it is called as the load resistance. The RE resistor is used for the thermal stability. The C1 capacitor is
used to separate the AC signals from the DC biasing voltage and the capacitor is known as the coupling
capacitor.

The figure shows that the bias vs gain common emitter amplifier transistor characteristics, if the R2 resistor
increases then there is an increase in the forward bias and R1 & bias are inversely proportional to each other.
The alternating current is applied to the base of the transistor of the common emitter amplifier circuit then there
is a flow of small base current. Hence there is a large amount of current flow through the collector with the help
of the RC resistance. The voltage near the resistance RC will change because the value is very high and the
values are from the 4 to 10kohm. Hence there is a huge amount of current present in the collector circuit which
amplified from the weak signal, therefore common emitter transistor work as an amplifier circuit.
OBJECTIVES:

 Discuss the operation of Common Emitter Voltage Divider configuration using Bipolar Junction
Transistor.

INSTRUMENTS AND COMPONENTS:

 1 Audio Generator / Function Generator  2 – 3.3 kΩ ¼ watts

 Variable DC Supply (0 – 30 Vdc)  2 – 1.2 kΩ ¼ watts
 Multimeter  2 – 1 microFarad / 25 V Electrolytic capacitor
 2 – 2N4123 or equivalent BJT Transistors  1 – 10 microFarad / 25 V Electrolytic capacitor
 2 – 39 kΩ ¼ watts  Connecting wires
 2 – 8.2 kΩ ¼ watts  Breadboard
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DIAGRAMS:

Figure 11.1

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 PROCEDURES:

5. Implement Figure 11.1 on the breadboard.

6. Using the Multimeter, measure VB, VC, VE, VCE, IB, IC, IE. Record the results in Table 11.1.
7. From the actual value of β = IC/IB, determine the value of Zi, Zo, AV, and output Voltage AC using the
measured value of input VI from the audio generator. Record the results in Table 11.1.

8. Compute the VB, VC, VE, VCE, IB, IC, IE, Zi, Zo, AV, and output voltage AC and record the results in Table
11.1.
OBTAINED RESULTS:
Table 11.1

Quantities Measured Values Computed Values

Voltage at the Base 700.411mV 19.3V

Voltage at the Collector 172.121V 20V

Voltage at the Emitter 0V 0V

Voltage at Collector-Emitter 8mV

Current at the Base 48.441µA 49.49µA

Current at the Collector 3.992mA 3.61mA

Current at the Emitter 3.31mA 0A

Input Impedance 0.5Ω

Output Impedance 5.6kΩ

Voltage Gain
Voltage Output AC 5.03V

COMPUTATIONS:

Vcc-VBE/RB = IB Ic = β IB = β(Vcc-VBE)/RB *KVL Ic= Vcc/ RC β= Ic/ IB

20-0.7/390k=49.49 µA Ic = β(49.49µA) = 3.57mA 20/5.6k=3.57mA 3.57mA/49.49µA = 72

VcE = Vcc- (IcRc) VE = 0V IE= (β+1) IB

20v-(3.57mA)(5.6k) =8mV (73)(49.49µA) =3.61mA

VcE=Vc-VE RE=25mV/IE *Zo= RC

VBE=VB-VE RE=25mV/3.61mA = 6.93Ω Zo=5.6KΩ
* VE= 0V *Zin= β(RE)
VBE=VB Zin=72(6.93Ω) =498.96Ω
VcE=Vc
 43
47 QUESTIONS:
1. What have you notice to the voltage gain if the by passed capacitor is disconnected?
Compare your answer to the results and explain.

We notice that the voltage gain will become 0 because the capacitor is disconnected.

2. Remove the 8.2 kilo ohms resistor in the network and determine the voltage gain. What
happen to the voltage gain?

If we remove the5.2k Ω resistor to the network the voltage gain will increase.

3. If the emitter resistor and capacitor are removed and connect the emitter junction to the
ground, what happen to the voltage gain? Compare your answer to the result and explain.

The Ve (voltage emitter) will become 0 but the voltage gain will have a value.

CONCLUSION: In this circuit we realize that th open circuit has zero total amount of voltage, because the
resistance cant pas with open switch.
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Date Performed:

ACTIVITY 12

COMMON BASE AMPLIFIER CONFIGURATION

INTRODUCTION:

The common base amplifier configuration is not widely used except in high frequency amplifiers where it has
some distinct advantages.

The common base amplifier is the least widely used of the three transistor amplifier configurations. The
common emitter and common collector (emitter follower) configurations are far more widely used because their
characteristics are generally more useful.

The common base amplifier configuration comes into its own at high frequencies where stability can be an
issue.

Common Base Transistor Amplifier Basics

For both NPN and PNP circuits, it can be seen that for the common
base amplifier circuit, the input is applied to the emitter, and the
output is taken from the collector. The common terminal for both
circuits is the base. The base is grounded for the signal and for this
reason the circuit may sometimes be called a grounded base circuit.

The common base amplifier configuration is not used as widely as

transistor amplifier configurations. However it does find uses with
amplifiers that require low input impedance levels. One application

is for moving-coil microphones preamplifiers - these microphones have very low impedance levels.

Another application is within VHF and UHF RF amplifiers where the low input impedance allows accurate
matching to the feeder impedance which is typically 50Ω or 75Ω. The configuration also improves stability
which is a key issue.

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It is worth noting that the current gain of a common-base amplifier is always less than unity.

However the voltage gain is more, but it is a function of input and output resistances (and also the internal
resistance of the emitter-base junction). As a result, the voltage gain of a common-base amplifier can be very

high.

OBJECTIVES:

 Discuss the operation of Common Base configuration using Bipolar Junction Transistor.
INSTRUMENTS AND COMPONENTS:  2 – 5.6 kΩ ¼ watts
 2 – 1.2 kΩ ¼ watts
 1 Audio Generator / Function Generator  2 – 1 microFarad / 25 V Electrolytic
 Variable DC Supply (0 – 30 Vdc) capacitor

 Multimeter  1 – 10 microFarad / 25 V Electrolytic

capacitor
 2 – 2N4123 or equivalent BJT
Transistors  Connecting wires

49
  Breadboard
DIAGRAMS:

Figure 12.1

PROCEDURES:

1. Implement Figure 12.1 on the breadboard.

2. Using the Multimeter, measure VB, VC, VE, VCE, IB, IC, IE. Record the results in Table 12.1.
3. From the actual value of β = I C/IB, determine the value of Zi, Zo, A V, and output Voltage AC using the
measured value of input VI from the audio generator. Record the results in Table 12.1.

4. Compute the VB, VC, VE, VCE, IB, IC, IE, Zi, Zo, AV, and output voltage AC and record the results in Table
12.1.

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 OBTAINED RESULTS:
Table 12.1

Quantities Measured Values Computed Values

Voltage at the Base 0V 0V
Voltage at the Collector 20V 19.656V
Voltage at the Emitter 5V 4.296V
Voltage at Collector-Emitter 1.048V
Current at the Base 0A 70µA
Current at the Collector 3.612mA 3.51mA
Current at the Emitter 4.776mA 3.58mA
Input Impedance 7.22 Ω
Output Impedance
Voltage Gain 771
Voltage Output AC 9.23V

COMPUTATIONS:
IE= IB + Ic IB=αIE α= Ic/ IE Ic= α IE
IB= IC – IE IB=(1-α)IE α=3.51mA/3.58mA=0.98 Ic=(0.98)(3.58mA)
IB=70µA Ic=3.51mA

KVL: -VEE + IERE + VCE + ICRC – VCC= 0 KVL: -VEE + IERE + VBE VE= IERE
VCE= VEE + VCE – 7 – ICRC- IERE IERE= VEE- VBE VE=(3.58mA)(1.2KΩ) =4.296V
VCE=(20+5)-[(3.58mA)(1.2KΩ)-(3.51mA)(5.6k)] IE= (VEE- VBE)/ RE
VCE=1.048V IE=(5-0.7)/1.2kΩ 1= 3.58mA

Re=26mV/ IE AV= Re/ re VC= ICRC

Re=26mV/3.58mA=7.26Ω AV=5.6kΩ/7.26Ω=771 VC=(3.51mA)(5.6k) =19.656V
*Zin= RE||re=re
*Zin=(7.26Ω)(1.2kΩ)/7.26+1.2kΩ = 7.22Ω

52 QUESTIONS:
1. What have you notice to the voltage gain? Compare the voltage gain to the voltage gain of the common
emitter fixed bias. What is the difference?

We notice that the voltage gain will decrease if it is the voltage gain of the common emitter fixed bias.
 2. What happen to the voltage collector (output voltage DC and AC) if the resistor at the collector junction is
open?

The voltage collector will represent its full voltage value, since the voltage doesn’t share any of its voltage
with a load. The voltage will equal to the amount of the supply.

CONCLUSION: Me and my group mates struggling in this circuit because in the question it will change the
direction and we notice that the voltage gain will change if we reverse the path into fixed bias.

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 Name, Course & Year : Rating:
Date Performed:

ACTIVITY 13

COMMON COLLECTOR AMPLIFIER CONFIGURATION

INTRODUCTION:

The emitter follower or common collector circuit provides an ideal buffer amplifier and it is easy to design the
circuit. It provides a high input impedance and a low output impedance.

This means that the emitter follower circuit provides an ideal buffer stage, and as a result it is used in many
circuits where there is a need not to load a circuit like an oscillator or other circuit, but provide a lower impedance
to the following stages.
The emitter follower is easy to design and implement, requiring just a few components.
The emitter follower transistor amplifier has a very straightforward circuit. The base is connected to the previous
stage, and often this may be directly connected as this can save on additional bias resistors which lower the input
impedance and hence increase the loading to the previous stage.

The emitter follower gains its name from the fact that the emitter follows the voltage on the base. It is actually
slightly less than the voltage on the base by the amount of the base emitter diode voltage drop. This also means
that the input and output are exactly in phase and not shifted by 180° as in the case of the common emitter
amplifier.

One key aspect of the characteristic is the input impedance. As it is normally used as a buffer amplifier, this
is the key parameter.

The input resistance can easily be calculated for a circuit because it is β times the resistor R1, where β is the
forward current gain of the transistor.

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 OBJECTIVES:

 Discuss the operation of Common

Collector configuration using Bipolar
Junction Transistor.
 2 – 270 kΩ ¼ watts
INSTRUMENTS AND COMPONENTS:  2 – 2.7 kΩ ¼ watts
 2 – 1 microFarad / 25 V Electrolytic
 1 Audio Generator / Function Generator capacitor
 Variable DC Supply (0 – 30 Vdc)  Connecting wires
 Multimeter  Breadboard
 2 – 2N4123 or equivalent BJT Transistors
DIAGRAMS:
The

54
 Figure 13.1

PROCEDURES:

1. Implement Figure 13.1 on the breadboard.

2. Using the Multimeter, measure VB, VC, VE, VCE, IB, IC, IE. Record the results in Table 13.1.
3. From the actual value of β = IC/IB, determine the value of Zi, Zo, AV, and output Voltage AC using the
measured value of input VI from the audio generator. Record the results in Table 13.1.

4. Compute the VB, VC, VE, VCE, IB, IC, IE, Zi, Zo, AV, and output voltage AC and record the results in Table
13.1.

55
 OBTAINED RESULTS:
Table 13.1

Quantities Measured Values Computed Values

Voltage at the Base 8.87 V 9.87V
Voltage at the Collector 20 V 20V
Voltage at the Emitter 9.11V 9.43V
Voltage at Collector-Emitter 9.971V 10.57V
Current at the Base 33.518mA 36.544µA
Current at the Collector 3.44mA 3.46mA

Current at the Emitter 3.61mA 3.49mA

Input Impedance 131k Ω
Output Impedance 7.16 Ω
Voltage Gain 1
Voltage Output AC 5.566V

COMPUTATIONS:
VCC- IBRB-VBE-IERE=0 VB= IBRB
IB= (VCC- VBE)/ RB+(β+1)(RE) VB=(36.544µA)(270kΩ)= 9.87V
IB=(20-0.7)/270kΩ+(94.605+1)(2.7kΩ)
IB=36.544µA

re=25mV/IE *Zin= RB||βRe Zout=re

re=25mV/3.49mA=7.16 Ω Zin=(94.605)(270kΩ)(2.7kΩ)/ 270kΩ+94.605+2.7kΩ=131k Ω Zout=7.16 Ω
VCE=20-IERE
VCE=20- (β+1)(IBRE) VE=(β+1)(IBRE) IE=(β+1)(IB)
VCE=20- (94.605+1)(36.544µA)(2.7kΩ) VE= (94.605+1)(36.544µA)(2.7kΩ)= 9.43V IE=(94.605+1)
VCE=10.57V IC= βIB ( 36.544µA)=3.49mA
IC=(94.605)(36.544µA)= 36.544µA
57 QUESTIONS:
1. What have you notice to the voltage gain if you transfer a 1 micro Farad/ 25V capacitor (output coupling
capacitor) at the collector junction from the emitter junction?

The voltage gain will increase because the 25V in the capacitor will add to the total amount of the voltage
in the capacitor.
 2. Compare the voltage gain of question number 1 to the result of your experiment/ What you have notice?
Why?

The result of our experiment has the total amount of 1V, but then when we Transfer the capacitor the total amount of the voltage gain
= 1.9V
So, the voltage gain will increase when we transfer the capacitor at the collector.

CONCLUSION:
If we transfer the capacitor with a vaue of a1 micro farad/25V the value of our voltage gain will be changed because the
capacitor has absorb 25V and it will add to the total amount of voltage gain passing the collector.

58