DEPARTMENT OF ELECTRONICS AND COMMUNICATION...
Transcript of DEPARTMENT OF ELECTRONICS AND COMMUNICATION...
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DEPARTMENT OF ELECTRONICS AND
COMMUNICATION ENGINEERING
LAB MANUAL
EC8261 CIRCUITS AND DEVICES LABORATORY
I YEAR/ II SEMESTER
REGULATION 2017
PREPARED BY
Mr S. Venkatraman AP/ECE
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VISION OF THE INSTITUTE
To Develop Globally Competitive Human Resource through Virtuous Enlightened Learning.
MISSION OF THE INSTITUTE
M1: To Impart Quality Technical Education and Research Orientation Enabling the Technocrats to
Fair Well in Global Competition.
M2: To Inculcate Committed Leadership Qualities through Ethical Practices.
M3: To Acquire Skills through Industry Practices and Develop the habit of life-long learning.
VISION OF THE DEPARTMENT
To Produce Competent and Responsible Engineers to meet the growing Challenges in the field of
Electronics and Communication Engineering
MISSION OF THE DEPARTMENT
M1: To impart strong technical competency to learners by using best pedagogical methods
M2: To provide industrial exposure to learners by collaboration with industries for training,
internships, and expert talks.
M3: To imbibe self-learning, collaborative learning, Ethical values and Environment awareness
through Co- curricular and Extra-curricular activities.
PROGRAMME EDUCATIONAL OBJECTIVES
PEO1: Adapt to dynamically evolving technologies for a successful career in an
academia/Industry/Entrepreneur
PEO 2: Apply the knowledge of Electronics and communication Engineering to solve real world
problems.
PEO 3: Exhibit effective communication skills and can perform as a team player with leadership
traits.
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PROGRAM OUTCOMES
Engineering Graduates will be able to:
1. Engineering knowledge: Apply the knowledge of mathematics, science, engineering
fundamentals, and an engineering specialization to the solution of complex engineering problems.
2. Problem analysis: Identify, formulate, review research literature, and analyze complex
engineering problems reaching substantiated conclusions using first principles of mathematics,
natural sciences, and engineering sciences.
3. Design/development of solutions: Design solutions for complex engineering problems and
design system components or processes that meet the specified needs with appropriate
consideration for the public health and safety, and the cultural, societal, and environmental
considerations.
4. Conduct investigations of complex problems: Use research-based knowledge and research
methods including design of experiments, analysis and interpretation of data, and synthesis of the
information to provide valid conclusions.
5. Modern tool usage: Create, select, and apply appropriate techniques, resources, and modern
engineering and IT tools including prediction and modeling to complex engineering activities with
an understanding of the limitations.
6. The engineer and society: Apply reasoning informed by the contextual knowledge to assess
societal, health, safety, legal and cultural issues and the consequent responsibilities relevant to the
professional engineering practice.
7. Environment and sustainability: Understand the impact of the professional engineering
solutions in societal and environmental contexts, and demonstrate the knowledge of, and need for
sustainable development.
8. Ethics: Apply ethical principles and commit to professional ethics and responsibilities and
norms of the engineering practice.
9. Individual and team work: Function effectively as an individual, and as a member or leader in
diverse teams, and in multidisciplinary settings.
10. Communication: Communicate effectively on complex engineering activities with the
engineering community and with society at large, such as, being able to comprehend and write 4
effective reports and design documentation, make effective presentations, and give and receive
clear instructions.
11. Project management and finance: Demonstrate knowledge and understanding of the
engineering and management principles and apply these to one‟s own work, as a member and
leader in a team, to manage projects and in multidisciplinary environments.
12. Life-long learning: Recognize the need for, and have the preparation and ability to engage in
independent and life-long learning in the broadest context of technological change.
PROGRAMME SPECIFIC OUTCOMES
PSO 1: Develop Innovative Ideas for an existing / Novel problem through Information and
Communication technologies.
PSO 2: Apply the Analog and Digital system Design Principles and practices for Developing
Quality products.
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EC8261 CIRCUITS AND DEVICES LABORATORYL T P C 0 0 4 2
OBJECTIVES:
To learn the characteristics of basic electronic devices such as Diode, BJT,FET, SCR
To understand the working of RL,RC and RLC circuits
To gain hand on experience in Thevinin & Norton theorem, KVL & KCL, and Super Position
Theorems
List of Experiments
1. Characteristics of PN Junction Diode
2. Zener diode Characteristics & Regulator using Zener diode
3. Common Emitter input-output Characteristics
4. Common Base input-output Characteristics
5. FET Characteristics
6. SCR Characteristics
7. Clipper and Clamper & FWR
8. Verifications Of Thevinin & Norton theorem
9. Verifications Of KVL & KCL
10. Verifications Of Super Position Theorem
11. verifications of maximum power transfer & reciprocity theorem
12. Determination Of Resonance Frequency of Series & Parallel RLC Circuits
13. Transient analysis of RL and RC circuits
TOTAL: 60 PERIODS
OUTCOMES:
At the end of the course, the student should be able to:
Analyze the characteristics of basic electronic devices
Design RL and RC circuits
Verify Thevinin & Norton theorem KVL & KCL, and Super Position Theorems
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COURSE OUTCOMES
COURSE
CODE
EC826
1
COURSE NAME CIRCUITS AND DEVICES
LAB
SEM 2
On completion of the course, the students will be able to
CO1 Demonstrate the VI characteristics of basic electronic devices
CO2 Construct the RL and RC circuits for transient analysis.
CO3 Verify the KVL, KCL, Thevenin, Nortton’.and superposition theorems.
CO4 Analyze the Frequency response of Series and Parallel RLC Circuits.
CO5 Construct the wave shaping circuits.
CO’S – PO’S & PSO’S MAPPING
CO/
PO
PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 PSO1 PSO2
CO1 3 3 2 1 2 2 1 3 3
CO2 3 3 2 1 2 2 1 3 3
CO3 3 3 3 1 2 2 1 3 3
CO4 3 3 3 1 2 2 1 3 3
CO5 3 3 3 1 2 2 1 3 3
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Table of contents
SL.No. NAME OF THE EXPERIMENT PAGE No.
1 Characteristics of PN Junction Diode
2 Zener diode Characteristics & Regulator using Zener diode
3 Common Emitter input-output Characteristics
4 Common Base input-output Characteristics
5 FET Characteristics
6 SCR Characteristics
7 Clipper and Clamper & FWR
8 Verifications Of Thevinin & Norton theorem
9 Verifications Of KVL & KCL
10 Verifications Of Super Position Theorem
11 verifications of maximum power transfer & reciprocity theorem
12 Determination Of Resonance Frequency of Series & Parallel RLC
Circuits
13 Transient analysis of RL and RC circuits
CONTENT BEYOND THE SYLLABUS
14 Study the V-I Characteristics of LED.
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CHARACTERISTICS OF PN JUNCTION DIODE
Diode schematic Symbol:
CIRCUIT DIAGRAM:
B) Forward bias:
C) Reverse Bias:
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EXP.No.01 CHARACTERISTICS OF PN JUNCTION DIODE
AIM:
To plot Volt-Ampere Characteristics of Silicon P-N Junction Diode.
To find cut-in Voltage for Silicon P-N Junction diode.
To find static and dynamic resistances in both forward and reverse biased conditions
for P-N Junction diode.
APPARATUS REQUIRED:
S.No. Name of the apparatus Range Quantity
1. P-N Diode IN4007 1No
2. Regulated Power supply (0-30V) 1No
3. Resistor 1KΩ 1No
4. Ammeter (0-20 mA) 1No
5. Ammeter (0-200μA) 1No.
6. Voltmeter (0-1V) 1No.
7. Voltmeter (0-20V) 1No.
8. Bread board - 1No.
9. Connecting wires Single strand As required
THEORY:
A P-N junction diode conducts only in one direction. The V-I characteristics of the diode
are curve between voltage across the diode and current flowing through the diode. When external
voltage is zero, circuit is open and the potential barrier does not allow the current to flow.
Therefore, the circuit current is zero. When Ptype (Anode) is connected to +ve terminal and n-
type (cathode) is connected to –ve terminal of the supply voltage is known as forward bias.
The potential barrier is reduced when diode is in the forward biased condition. At some forward
voltage, the potential barrier altogether eliminated and current starts flowing through the diode and
also in the circuit. Then diode is said to be in ON state. The current increases with increasing V f.
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MODEL GRAPH:
1. Take a graph sheet and divide it into 4 equal parts. Mark origin at the center of the graph sheet.
2. Now mark +ve X-axis as Vf, -ve X-axis as Vr, +ve Y-axis as If and –ve Y-axis as Ir.
3. Mark the readings tabulated for Si forward biased condition in first Quadrant and Si reverse
biased condition in third Quadrant.
OBSERVATIONS:
A) FORWARD BIAS:
S.No. Applied Voltage(V) Forward Voltage(Vf) Forward Current(If(mA))
B) REVERSE BIAS:
S.No. Applied Voltage(V) Forward Voltage(Vr) Reverse Current((IR(μA))
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Calculations:
In forward bias condition:
Static Resistance, Rs = Vf/If =
Dynamic Resistance, RD = ΔVf/ ΔIf =
In Reverse bias condition:
Static Resistance, Rs = VR/IR =
Dynamic Resistance, RD = ΔVR/ ΔIR =
When N-type (cathode) is connected to +ve terminal and P-type (Anode) is connected -ve
terminal of the supply voltage is known as reverse bias and the potential barrier across the
junction increases. Therefore, the junction resistance becomes very high and a very small current
(reverse saturation current) flows in the circuit. Then diode is said to be in OFF state. The reverse
bias current is due to minority charge carriers.
PROCEDURE:
A) FORWARD BIAS:
1. Connections are made as per the circuit diagram.
2. For forward bias, the RPS +ve is connected to the anode of the diode and RPS –ve is connected
to the cathode of the diode
3. Switch on the power supply and increase the input voltage (supply voltage) in steps of 0.1V.
4. Note down the corresponding current flowing through the diode and voltage across the diode for
each and every step of the input voltage.
5. The reading of voltage and current are tabulated.
6. Graph is plotted between voltage (Vf) on X-axis and current (If) on Y-axis.
B) REVERSE BIAS:
1. Connections are made as per the circuit diagram
2. For reverse bias, the RPS +ve is connected to the cathode of the diode and RPS –ve is connected
to the anode of the diode.
3. Switch on the power supply and increase the input voltage (supply voltage) in steps of 1V.
4. Note down the corresponding current flowing through the diode voltage across the diode for
each and every step of the input voltage.
5. The readings of voltage and current are tabulated
6. Graph is plotted between voltage(VR) on X-axis and current (IR) on Y-axis.
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PRECAUTIONS:
1. While doing the experiment do not exceed the readings of the diode. This may lead to
damaging of the diode.
2. Connect voltmeter and ammeter in correct polarities as shown in the circuit diagram.
3. Do not switch ON the power supply unless you have checked the circuit connections as per the
circuit diagram.
RESULT:
Thus the V-I characteristics of PN junction diode was plotted and determined its cut in voltage,
static and dynamic resistances in forward and reverse bias condition.
Forward Bias of PN Junction Diode:
The Cut in Voltage or Knee Voltage (Vγ) is _____________Volts.
The Dynamic Forward resistance is __________________ Ω.
The Static Forward resistance is __________________ Ω.
Reverse Bias of PN Junction Diode:
The Dynamic Reverse resistance is _________________ Ω.
The Static Reverse resistance is _________________ Ω.
VIVA QUESTIONS:
1. Define depletion region of a diode.
2. What is meant by transition & space charge capacitance of a diode?
3. Is the V-I relationship of a diode Linear or Exponential?
4. Define cut-in voltage of a diode and specify the values for Si and Ge diodes.
5. What are the applications of a p-n diode?
6. Draw the ideal characteristics of P-N junction diode.
7. What is the diode equation?
8. What is PIV?
9. What is the break down voltage?
10. What is the effect of temperature on PN junction diodes?
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ZENER DIODE CHARACTERISTICS
Diode schematic Symbol
CIRCUIT DIAGRAM
A) FORWARD BIAS CHARACTERISTICS:
A) REVERSE BIAS CHARACTERISTICS:
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EXP.No.02 ZENER DIODE CHARACTERISTICS & REGULATOR USING ZENER DIODE
AIM:
To plot the volt ampere characteristics of a zener diode.
To determine its knee voltage, breakdown voltage also its static and dynamic
resistances in forward and reverse bias.
To determine the line and load regulation characteristics of a zener diode.
APPARATUS REQUIRED:
S.No. Name of the apparatus Range Quantity
1 Zener diode IZ6 1No
2 Regulated Power supply (0-30V) 1No
3 Resistor 1KΩ 1No
4 Ammeter (0-1000µA) 1No
5 Ammeter (0-100 mA) 1No
6 Ammeter (0-200 mA) 2Nos
7 Voltmeter (0-1V) 1No
8 Voltmeter (0-20V) 1No
9 Decade Resistance Box (DRB) 1 No
10 Bread board - 1No
11 Connecting wires Single strand As required
THEORY:
A zener diode is heavily doped p-n junction diode, specially made to operate in the break
down region. A p-n junction diode normally does not conduct when reverse biased. But if the
reverse bias is increased, at a particular voltage it starts conducting heavily.
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MODEL GRAPH:
OBSERVATIONS:
A) FORWARD BIAS:
S.NO Applied Voltage(V) Forward Voltage(Vf) Forward Current(If(mA))
B) REVERSE BIAS:
S.NO Applied Voltage(V) Forward Voltage(Vr) Reverse Current((IR(μA))
CALCULATIONS:
Forward bias
Static forward resistance Rdc = Vf / If Ω
Dynamic forward resistance rac = ΔVf/ΔIf Ω
Reverse bias
Static reverse resistance Rdc = Vr/ Ir Ω
Dynamic reverse resistance rac = ΔVf/ΔIf Ω
For Load Regulation, % Voltage Regulation = (𝑉𝑁𝐿−𝑉𝐹𝐿)
𝑉𝐹𝐿 X 100
This voltage is called Break down Voltage. High current through the diode can
permanently damage the device. Applying a positive potential to the anode and a negative potential
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to the cathode of the zener diode establishes a forward bias condition. The forward characteristic
of the zener diode is same as that of a pn junction diode i.e. as the applied potential increases the
current increases exponentially. Applying a negative potential to the anode and positive potential
to the cathode reverse biases the zener diode.
As the reverse bias increases the current increases rapidly in a direction opposite to that of
the positive voltage region. Thus under reverse bias condition breakdown occurs. It occurs because
there is a strong electric filed in the region of the junction that can disrupt the bonding forces
within the atom and generate carriers. The breakdown voltage depends upon the amount of doping.
For a heavily doped diode depletion layer will be thin and breakdown occurs at low reverse
voltage and the breakdown voltage is sharp. Whereas a lightly doped diode has a higher
breakdown voltage. This explains the zener diode characteristics in the reverse bias region.
Basically there are two types of regulations such as:
Line Regulation: In this type of regulation, series resistance and load resistance are fixed,
only input voltage is changing. Output voltage remains the same as long as the input
voltage is maintained above a minimum value.
Load Regulation: In this type of regulation, input voltage is fixed and the load resistance
is varying. Output volt remains same, as long as the load resistance is maintained above a
minimum value.
PROCEDURE:
1) V- I CHARACTERISTICS:
a) Forward Bias Condition:
1. Connect the circuit as shown in figure .
2. Initially vary Vs in steps of 0.1V. Once the current starts increasing vary Vs in steps of 1V
up to 12V. Note down the corresponding readings of Vzf and Izf.
b) Reverse Bias Condition:
1. Connect the circuit as shown in figure (2).
2. Vary Vs gradually in steps of 1V up to 12V and note down the corresponding readings of
Vzr and Izr.
3. Tabulate different reverse currents obtained for different reverse voltages.
ZENER DIODE REGULATION CHARACTERISTICS
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A) LINE REGULATION:
MODEL GRAPH:
TABULATION:
Load resistance RL = KΩ
Sl.No. Input Supply
Voltage Vs
Zener current Iz
(mA)
Load current IL
(mA)
Regulated output
voltage Vo (V)
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2) Regulation characteristics:
a) Line Regulation
1. Connect the circuit for line regulation as shown in the figure.
2. Vary supply voltage (Vs) in steps of 1V from 0-15 Volts and note the corresponding
zener current (Iz), load current (IL) and output voltage (Vo).
3. Plot the graph between Vs and Vo taking Vs on X axis and Vo on Yaxis.
b) Load Regulation:
1. Connect the circuit for Load regulation as shown in figure .
2. Now fix the power supply voltage, Vs at 10V.
3. Without connecting the load RL, note down the No-Load Voltage (VNL).
4. Now connect the load (RL) using Decade Resistance Box (DRB) and vary the resistance in
steps 1K from 1K to10K / in steps of 10 K from10K to 100K and note the
corresponding Zener Current (IZ), Load Current (IL) and Output Voltage (VO) for 10
readings and calculate the percentage regulation.
5. Plot the graph between RL and VO taking RL on X-axis and VO on Y-axis.
PRECAUTIONS:
1. The terminals of the zener diode should be properly identified
2. While determined the load regulation, load should not be immediately shorted.
3. Should be ensured that the applied voltages & currents do not exceed the ratings of the diode.
RESULT:
Thus plotted the VI characteristics of Zener diode and determined its parameters:
a) Forward Bias Zener Diode:
1. The Knee voltage or Cut-in Voltage (Vy) is __________________ Volts.
2. The Dynamic Forward resistance is __________________ Ω.
3. The Static Forward resistance is __________________ Ω..
b) Reverse Bias of Zener Diode:
1. Zener Breakdown Voltage (VZ) is ____________________ Volts.
2. The Dynamic Reverse resistance is __________________ Ω
3. The Static Reverse resistance is __________________ Ω.
The percentage regulation of the Zener Diode is _______
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B) LOAD REGULATION:
MODEL GRAPH:
TABULATION:
Input supply voltage Vs = Volts
No load DC voltage, VNL = Volts
Sl.No Load resistance
RL (KΩ)
Zener current
Iz (mA)
Load current
IL (mA)
Output voltage
Vo (Volts)
% Voltage
regulation
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VIVAQUESTIONS:
1. What type of temp coefficient does the zener diode have?
2. If the impurity concentration is increased, how does the depletion width get effected?
3. Does the dynamic impendence of a zener diode vary?
4. Explain briefly about avalanche and zener breakdowns.
5. Draw the zener equivalent circuit.
6. Differentiate between line regulation & load regulation.
7. Which region zener diode can be used as a regulator?
8. How the breakdown voltage of a particular diode can be controlled?
9. What type of temperature coefficient does the Avalanche breakdown has?
10. By what type of charge carriers the current flows in zener and avalanche breakdown diodes?
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COMMON EMITTER INPUT-OUTPUT CHARACTERISTICS
SYMBOL:(NPN TRANSISTOR)) PIN DIAGRAM: (BOTTOM VIEW)
CIRCUIT DIAGRAM:
INPUT CHARACTERISTICS
OUTPUT CHARACTERISTICS
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EXP.No.02 COMMON EMITTER INPUT-OUTPUT CHARACTERISTICS
AIM:
To draw the input and output characteristics of transistor connected in CE configuration
To find β of the given transistor and also its h parameters.
APPARATUS REQUIRED:
S.No. Name of the apparatus Range Quantity
1. Transistor BC107 1No
2. Dual Regulated Power supply (0-30V) 1No
3. Resistor 1KΩ 1No
4. Ammeter (0-30 mA) 1No
5. Ammeter (0-1000μA) 1No
6. Voltmeters (0-20V) , (0-1)V, (0-10)V Each 1No
7. Bread board - 1 No
8. Connecting wires Single strand As required
THEORY:
In common emitter configuration, input voltage is applied between base and emitter
terminals and output is taken across the collector and emitter terminals. Therefore the emitter
terminal is common to both input and output. The input characteristics resemble that of a forward
biased diode curve. This is expected since the Base-Emitter junction of the transistor is forward
biased. As compared to CB arrangement IB increases less rapidly with VBE. Therefore input
resistance of CE circuit is higher than that of CB circuit. The output characteristics are drawn
between Ic and VCE at constant IB. the collector current varies with VCE up to few volts only.
After this the collector current becomes almost constant, and independent of VCE. The value of
VCE up to which the collector current changes with V CE is known as Knee voltage. The
transistor always
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MODEL GRAPH:
A) INPUT CHARACTERISTICS:
B) OUTPUT CHARACTERSITICS:
Calculations:
1. Input Characteristics: To obtain input resistance find VBE and IB for a constant VCE
on one of the input characteristics.
Input impedance = hie= Ri = VBE/ IB(VCEis constant)
Reverse voltage gain = hre= VEB/ VCE(IB= constant)
2. Output Characteristics: To obtain output resistance find ICand VCBat aconstant IB.
Output admittance 1/hoe = Ro = IC/ VCE(IBis constant)
Forward current gain = hfe = IC/ IB(VCE= constant)
3. Current amplification factor β = ΔIC/ΔIB
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Operated in the region above Knee voltage, IC is always constant and is approximately equal
to IB.The current amplification factor of CE configuration is given by
β = ΔIC/ΔIB
Input Resistance, ri = ΔVBE /ΔIB (μA) at Constant VCE
Output Résistance, ro = ΔVCE /ΔIC at Constant IB (μA)
PROCEDURE:
A) INPUT CHARACTERISTICS
1. Connect the circuit as per the circuit diagram.
2. For plotting the input characteristics the output voltage VCE is kept constant at 1V and for
different values of VBB , note down the values of IB and VBE
3. Repeat the above step by keeping VCE at 2V and 4V and tabulate all the readings.
4. Plot the graph between VBE and IB for constant VCE
B) OUTPUT CHARACTERISTICS:
1. Connect the circuit as per the circuit diagram
2. For plotting the output characteristics the input current IB is kept constant at 50μA and for
different values of VCC note down the values of IC and VCE
3. Repeat the above step by keeping IB at 75 μA and 100 μA and tabulate the all the readings
4. Plot the graph between VCE and IC for constant IB
PRECAUTIONS:
1. The supply voltage should not exceed the rating of the transistor
2. Meters should be connected properly according to their polarities
RESULT:
Thus obtained the input and output characteristics of transistor connected in CE
configuration and determined its parameters as follows.
Input impedance = hie= Ri =
Reverse voltage gain = hre=
Output admittance 1/hoe = Ro =
Forward current gain = hfe =
Current amplification factor β =
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TABULATION:
Input Characteristics
VBB (Volts)
VCE = 0V VCE = 5V
VBE
(Volts)
IB
(µA)
VBE
(Volts)
IB
(µA)
Output Characteristics
VCC
(Volts)
IB = 0 µA IB = 20 µA IB = 40 µA
VCE
(Volts)
IC
(mA)
VCE
(Volts)
IC
(mA)
VCE
(Volts)
IC
(mA)
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VIVA QUESTIONS:
1. What is the range of β for the transistor?
2. What are the input and output impedances of CE configuration?
3. Identify various regions in the output characteristics.
4. What is the relation between α and β?
5. Define current gain in CE configuration.
6. Why CE configuration is preferred for amplification?
7. What is the phase relation between input and output?
8. Draw diagram of CE configuration for PNP transistor.
9. What is the power gain of CE configuration?
10. What are the applications of CE configuration?
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COMMON BASE INPUT-OUTPUT CHARACTERISTICS
SYMBOL: (NPN TRANSISTOR)) PIN DIAGRAM: (BOTTOM VIEW)
CIRCUIT DIAGRAM:
INPUT CHARACTERISTICS
OUTPUT CHARACTERISTICS
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EXP.No.04 COMMON BASE INPUT-OUTPUT CHARACTERISTICS
AIM:
To observe and draw the input and output characteristics of a transistorconnected in
common base configuration.
To find α of the given transistor and also its h parameters.
APPARATUS REQUIRED:
S.No Name of the apparatus Range Quantity
1 Transistor BC107 1No
2 Regulated Power supply (0-30V) 1No
3 Resistor 1KΩ 2No
4 Ammeters (0-100 mA) 2No
5 Voltmeters (0-20V), (0-1)V 2Nos, 1 No
6 Bread board - 1 No
7 Connecting wires Single strand As required
THEORY:
A transistor is a three terminal active device. The terminals are emitter, base, collector. In
CB configuration, the base is common to both input (emitter) and output (collector). For normal
operation, the E-B junction is forward biased and C-B junction is reverse biased. In CB
configuration, IE is +ve, IC is –ve and IB is –ve. So,
VEB = F1 (VCB, IE) and
IC = F2 (VEB,IB)
With an increasing the reverse collector voltage, the space-charge width at the output
junction increases and the effective base width „W‟ decreases. This phenomenon is known as
“Early effect”. Then, there will be less chance for recombination within the base region. With
increase of charge gradient with in the base region, the current of minority carriers injected across
the emitter junction increases. The current amplification factor of CB configuration is given by,
EXPECTED GRAPHS:
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A) INPUT CHARACTERISTICS:
B) OUTPUTCHARACTERISTICS
CALCULATIONS:
1. Input Characteristics: To obtain input resistance, find VEE and IE for a constant VCB
on one of the input characteristics.
Input impedance = hib = Ri = VEE / IE (VCB = constant)
Reverse voltage gain = hrb = VEB / VCB (IE = constant)
2. Output Characteristics: To obtain output resistance, find IC and VCB at a constant IE.
Output admittance = hob = 1/Ro = IC / VCB (IE = constant)
Forward current gain = hfb = IC / IE (VCB = constant)
3. Current amplification factor α = ΔIC/ ΔIE
α = ΔIC/ ΔIE
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Input Resistance, ri = ΔVBE /ΔIEat Constant VCB
Output Résistance, ro = ΔVCB /ΔICat Constant IE
PROCEDURE:
A) INPUT CHARACTERISTICS:
1. Connections are made as per the circuit diagram.
2. For plotting the input characteristics, the output voltage VCE is kept constant at 0V and for
different values of VEE ,note down the values of IE and VBE
3. Repeat the above step keeping VCB at 2V, 4V, and 6V and all the readings are tabulated.
4. A graph is drawn between VEB and IE for constant VCB.
B) OUTPUT CHARACTERISTICS:
1. Connections are made as per the circuit diagram.
2. For plotting the output characteristics, the input IE is kept constant at 0.5mA and for different
values of VCC, note down the values of IC and VCB.
3. Repeat the above step for the values of IE at 1mA, 5mA and all the readings are tabulated.
4. A graph is drawn between VCB and Ic for constant IE
PRECAUTIONS:
1. The supply voltages should not exceed the rating of the transistor.
2. Meters should be connected properly according to their polarities.
RESULT:
Thus obtained the input and output characteristics of transistor connected in CB
configuration and determined its parameters as follows.
Input impedance = hib = Ri =
Reverse voltage gain = hrb =
Output admittance = hob = 1/Ro =
Forward current gain = hfb =
Current amplification factor α = ΔIC/ ΔIE
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TABULATION:
Input Characteristics
VEE (Volts)
VCB = 0V VCB = 4V
VEB (Volts) IE (mA) VEB (Volts) IE (mA)
Output Characteristics
VCC
(Volts)
IE = 0mA IE = 5V IE = 10mA
VCB
(Volts)
IC
(mA)
VCB
(Volts)
IC
(mA)
VCB
(Volts)
IC
(mA)
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VIVA QUESTIONS:
1. What is the range of α for the transistor?
2. Draw the input and output characteristics of the transistor in CB configuration.
3. Identify various regions in output characteristics.
4. What is the relation between α and β?
5. What are the applications of CB configuration?
6. What are the input and output impedances of CB configuration?
7. Define α (alpha).
8. What is early effect?
9. Draw Circuit diagram of CB configuration for PNP transistor.
10. What is the power gain of CB configuration?
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JFET CHARACTERISTICS
SYMBOL PIN DIAGRAM:
CIRCUIT DIAGRAM:
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EXP.No.05 FET CHARACTERISTICS
AIM:
To determine the drain & transfer characteristics of given JFET & to find its parameters.
APPARATUS REQUIRED:
THEORY:
Operation:
The circuit diagram for studying drain and transfer characteristics is shown in the fig.
1. Drain characteristics are obtained between the drain to source voltage (VDS)
and drain current (ID) taking gate to source voltage (VGS) as the constant
parameter.
2. Transfer characteristics are obtained between the gate to source voltage (VGS)
and drain current (ID) taking drain to source voltage (VDS) as the constant
parameter.
S.No Name of the apparatus Range Quantity
1 FET BFW 10 1No
2 Dual Regulated Power supply (0-30V) 1No
3 Resistor 1KΩ, 100KΩ Each 1No
4 Ammeters (0-200 mA) 1No
5 Voltmeters (0-20V) 2Nos.
6 Bread board - 1 No
7 Connecting wires Single strand As required
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EXPECTED GRAPHS:
A) DRAIN CHARACTERISTICS
B) TRANSFER CHARACTERISTICS:
CALCULATION:
1. Drain resistance (rd) = ΔVDS/ΔID
2. Trans conductance (gm) = ΔID/ΔVGS
3. Amplification factor (μ) =rd*gm.
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PROCEDURE:
DRAIN CHARACTERISTICS:
1. Connections are made as per the circuit diagram.
2. Set gate voltage VGS=-1, vary the drain voltage VDS instep of 1V & note down the
corresponding drain current ID.
3. Repeat the above procedure for VGS=0V,-2V. 4. Plot the graph for a constant VDS Vs ID
5. Find the drain resistance (rd) = ΔVDS/ΔID
TRANSFER CHARACTERISTICS:
1. Connections are made as per the circuit diagram.
2. Set gate voltage VDS=1V, vary the gate voltage VGS in step of 1V and note down the
corresponding drain current ID
3. Repeat the above procedure for VDS=5V, 10V.
4. Plot the graph for VGS Vs ID.
5. Find the Trans conductance (gm) gm = ΔID/ΔVGS
RESULT:
Thus the drain and transfer characteristics of JFET is drawn and the parameters were
determined.
1. Drain resistance (rd) =…………
2. Trans conductance (gm) =…………
3. Amplification factor (μ) =………...
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VIVA QUESTIONS:
1. Why FET is called as VVR?
2. What is unipolar device?
3. What is the advantage of high input resistance in FET?
4. List the applications of FET Device.
5. Mention the merits and demerits of FET compared to BJT.
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SCR CHARACTERISTICS
SYMBOL PIN DIAGRAM
CIRCUIT DIAGRAM:
V-I CHARACTERISTICS:
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EXP.No.06 SILICON-CONTROLLED RECTIFIER (SCR) CHARACTERISTICS
AIM:
To obtain the V-I Characteristics of SCR and also to determine the break over voltage and holding
current.
APPARATUS REQUIRED:
S.No. Name of the apparatus Range Quantity
1. SCR TYN616 1No
2. Dual Regulated Power supply (0-30V) 1No
3. Resistor 10KΩ,1KΩ Each 1
4. Ammeters (0-50) mA 1No
5. Voltmeters (0-10V) 1No
6. Bread board - 1 No
7. Connecting wires Single strand As required
THEORY:
It is a four layer semiconductor device being alternate of P-type and N-type silicon. It
consists of 3 junctions J1, J2, J3 the J1 and J3 operate in forward direction and J2 operates in
reverse direction and three terminals called anode A, cathode K , and a gate G. The operation of
SCR can be studied when the gate is open and when the gate is positive with respect to cathode.
When gate is open, no voltage is applied at the gate due to reverse bias of the junction J2 no
current flows through R2 and hence SCR is at cut off. When anode voltage is increased J2 tends to
breakdown. When the gate positive, with respect to cathode J3 junction is forward biased and J2 is
reverse biased .Electrons from N-type material move across junction J3 towards gate while holes
from P-type material moves across junction J3 towards cathode. So gate current starts flowing,
anode current increase is in extremely small current junction J2 break down and SCR conducts
heavily.
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OBSERVATION:
VAK(V) IAK ( μA)
When gate is open thee break over voltage is determined on the minimum forward voltage
at which SCR conducts heavily. Now most of the supply voltage appears across the load
resistance. The holding current is the maximum anode current gate being open, when break over
occurs.
PROCEDURE:
1. Connections are made as per circuit diagram.
2. Keep the gate supply voltage at some constant value
3. Vary the anode to cathode supply voltage and note down the readings of voltmeter and ammeter.
Keep the gate voltage at standard value.
4. A graph is drawn between VAK and IAK.
5. From the graph note down the threshold voltage and Holding current values.
CALCULATIONS:
Threshold Voltage =
Holding Current =
RESULT:
The V-I Characteristics of the SCR have been plotted.
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VIVA QUESTIONS:
1. What the symbol of SCR?
2. In which state SCR turns of conducting state to blocking state?
3. What are the applications of SCR?
4. What is holding current?
5. What are the important types thyristors?
6. How many numbers of junctions are involved in SCR?
7. What is the function of gate in SCR?
8. When gate is open, what happens when anode voltage is increased?
9. What is the value of forward resistance offered by SCR?
10. What is the condition for making from conducting state to non conducting state?
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EXP.No.07CLIPPER AND CLAMPER & FWR
AIM:
To design a Clipping circuit for the given specifications and also plot the graph..
APPARATUS REQUIRED:
S.No. Name of the apparatus Range Quantity
1. Regulated Power supply (0-30V) 1No
2. Resistor 1Kohm 1No
3. Capacitor 1No
4. Diode IN 4007 1No
5. CRO 1No
6. Function Generator 1No
7. Multimeter 1No
8. Bread board 1No
9. Connecting wires 1No
Circuit Diagram:-
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Series Clippers
a) To pass –ve peak above Vr level :-
c) To pass +ve peak above Vr level :-
Clamper circuit:
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PROCEDURE: -
1. Connections are made as shown in the circuit diagram.
2. A sine wave Input Vi whose amplitude is greater than the clipping level is applied.
3. Output waveform Vo is observed on the CRO.
4. Clipped voltage is measured and verified with the designed values.
Viva Questions:
1. What is the need of wave shaping circuit in electronic?
2. What type of energy is stored in capacitor and inductor?
3. List the applications of clipper and clamper circuits.
4. Mention the role of clamper in real time application.
EXP. No. 08 (A) VERIFICATION OF THEVENIN’S THEOREM
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AIM:
To verify Thevenin theorem and to find the current flowing through the load resistance.
APPARATUS REQUIRED:
S.No Name of the apparatus Range Quantity
10. Regulated Power supply (0-30V) 1No
11. Resistor 2.2KΩ,1KΩ Each 1
12. Resistor 3.3KΩ,2.7KΩ Each 1
13. Ammeters (0-5) mA 1No
14. Voltmeters (0-5V) 1No
15. Bread board
16. Connecting wires
THEORY:
Thevenin`s theorem:
Any linear active network with output terminals can be replaced by a single voltage source
Vth in series with a single impedance Zth. Vth is the Thevenin`s voltage. It is the voltage between
the terminals on open circuit condition, Hence it is called open circuit voltage denoted by Voc. Zth
is called Thevennin`s impedance. It is the driving point impedance at the terminals when all
internal sources are set to zero too.
If a load impedance ZL is connected across output terminals, we can find the current
through it IL = Vth/ (Zth + ZL).
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CIRCUIT DIAGRAM:
EQUVALENT CIRCUIT:
TABULATION:
Vth Rth IL(mA)
Theoretical Practical Theoretical Practical Theoretical Practical
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PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Check your connections before switch on the supply.
3. Find the Thevenin’s voltage (or) open circuit voltage.
4. Replace voltage source by internal resistor.
5. Determine the Thevenin’s resistance.
6. Find IL by using Thevenin’s formula.
7. Compare the observation reading to theoretical value.
8. switch off the supply
9. Disconnect the circuit.
RESULT:
Thus the Thevenin’s theorem was verified.
Theoretical: Practical:
Vth = Vth =
Rth = Rth =
IL = IL =
B)VERIFICATION OF NORTON’S THEOREM
AIM:
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To verify Norton’s theorem and to determine the current flow through the load resistance.
COMPONENTS REQUIRED:
S.No Name of the apparatus Range Quantity
1. Regulated Power supply (0-15V) 1No
2. Resistor 10KΩ,5.6KΩ Each 1
3. Resistor 8.2KΩ,6KΩ Each 1
4. Ammeters (0-10) mA,mc 1No
5. Ammeters (0-5)mA,mc 1No
6. Bread board
7. Connecting wires
Norton’s theorem:
Any linear active network with output terminals can be replaced by a single current source.
Isc in parallel with a single impedance Zth. Isc is the current through the terminals of the active
network when shorted. Zth is called Thevennin`s impedance.
Current through RL= Isc Zth/( Zth+ZL)
CIRCUIT DIAGRAM:
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NORTON`S EQUIVALENT CIRCUIT:
TABULATION:
Theoretical Practical
Isc
Rth
Isc
Rth
PROCEDURE:
1. Connections are made as per the circuit diagram.
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2. Check your connections before switch on the supply.
3. Find the Norton’s current (or) short circuit current in load resistance.
4. Replace voltage source by internal resistor.
5. Determine the equivalent’s resistance.
6. Find IL by using Norton’s formula.
7. Compare the observation reading to theoretical value.
8. Switch off the supply
9. Disconnect the circuit.
RESULT:
Thus the Norton’s theorem was verified.
Theoretical: Practical:
Isc = Isc =
Rth = Rth =
IL = IL =
Viva Questions:
1. State thevenin theorem.
2. What is the need of thevenin & Norton theorem?
3. List the application of these twotheorems.
4. Define voltage and current division rule.
EXP.No.09 VERIFICATIONS OF KVL & KCL
AIM:
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To verify (i) kirchoff’s current law (ii) kirchoff’s voltage law
(i) KIRCHOFF’S CURRENT LAW:
COMPONENTS REQUIRED:
S.No. Name of the apparatus Range Quantity
1. Regulated Power supply (0-15V) 1No
2. Resistor 1KΩ 3No
3. Ammeters (0-10) mA,mc 3No
4. Bread board 1No
5. Connecting wires As
required
THEORY:
Krichoff’s current law: The algebraic sum of the currents entering in any node is Zero. The
law represents the mathematical statement of the fact change cannot accumulate at a node. A node
is not a circuit element and it certainly cannot store destroy (or) generate charge. Hence the current
must sum to zero. A hydraulic analog sum is zero. For example consider three water pipes joined
pn the shape of Y. we defined free currents as following into each of 3 pipes. If we insists that
what is always
CIRCUIT DIAGRAM:
1. Kirchhoff’s current law:
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Practical measurement:
TABULATION:
Voltage (V) Total current I(mA) I1(mA) I2(mA)
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Check your connections before switch on the supply.
3. Vary the regulated supply.
4. Measure the current using ammeter.
5. Note the readings in the tabulation.
6. Compare the observation reading to theoretical value.
ii) KIRCHOFF’S VOLTAGE LAW:
COMPONENTS REQUIRED:
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THEORY:
(i) Kirchhoff’s voltage law
The algebraic sum of the voltage around any closed path is zero. The law represents the
mathematical statement of the fact change cannot accumulate at a node. A node is not a circuit
element and it certainly cannot store destroy (or) generate charge. Hence the current must sum to
zero. A hydraulic analog sum is zero. For example consider three water pipes joined pn the shape
of Y. we defined free currents as following into each of 3 pipes. If we insists that what is always
CIRCUIT DIAGRAM:
Krichoff’s voltage law:
Kirchoff`s voltage law
Practical measurement:
Practical measurement
S.No. Name of the apparatus Range Quantity
1. Regulated Power supply (0-15V) 1No
2. Resistor 1KΩ,2.2KΩ, 3.3
KΩ
Each 1
3. Voltmeter (0-20) V, 3No
4. Bread board 1No
5. Connecting wires As required
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TABULATION:
Voltage (V) V1 (volts) V2 (volts) V3 (volts)
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Check your connections before switch on the supply.
3. Vary the regulated supply.
4. Measure the voltage using voltmeter.
5. Note the readings in the tabulation.
6. Compare the observation reading to theoretical value.
RESULT:
Thus the Kirchhoff’s current law and voltage law were verified.
EXP.No.10 VERIFICATIONS OF SUPER POSITION THEOREM
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AIM:
To verify the superposition theorem and also to determine the current following through the
load resistance.
APPARATUS REQUIRED:
Superposition theorem
In a linear circuit containing more than one source, the current that flows at any point or the
voltage that exists between any two points is the algebraic sum of the currents or the voltages that
would have been produced by each source taken separately with all other sources removed.
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Check your connections before switch on the supply.
3. Determine the current through the load resistance.
4. Now one of the sources is shorted and the current flowing through the resistance IL measured by
ammeter.
5. Similarly, the other source is shorted and the current flowing through the resistance IL measured
by ammeter.
6. Compare the value obtained with the sum of I1&I2 should equal to I
7. Compare the observation reading to theoretical value.
8. Switch off the supply.
9. Disconnect the circuit.
S.No. Name of the apparatus Range Quantity
1. Regulated Power supply (0-15V) 1No
2. Resistor 1KΩ,220KΩ,
470 KΩ
Each 1
3. Voltmeter (0-5) V, 1No
4. Ammeters (0-1)mA,mc 1No
5. Bread board 1No
6. Connecting wires As required
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Circuit diagram
Superposition
Tabulation:
V(volt) I1(mA) I2(mA) I3(mA)
V1 V2 Theoretical Practical Theoretical Practical Theoretical Practical
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Check your connections before switch on the supply.
3. Determine the current through the load resistance.
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4. Now one of the sources is shorted and the current flowing through the resistance IL measured by
ammeter.
5. Similarly, the other source is shorted and the current flowing through the resistance IL measured
by ammeter.
6. Compare the value obtained with the sum of I1&I2 should equal to I
7. Compare the observation reading to theoretical value.
8. Switch off the supply
9. Disconnect the circuit.
RESULT:
Thus the superposition theorem was verified.
EXP. No. 11 VERIFICATIONS OF MAXIMUM POWER TRANSFER & RECIPROCITY
THEOREM
AIM:
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To find the value of resistance RL in which maximum power is transferred to the load
resistance.
APPARATUS REQUIRED:
Maximum power transfer theorem:
Maximum power transfer to the load resistor occurs when it has a value equal to the
resistance of the network looking back at it from the load terminals.
CIRCUIT DIAGRAM:
MODEL GRAPH:
S.No. Name of the apparatus Range Quantity
1. Regulated Power supply (0-30V) 1No
2. Resistor 1KΩ,2.2KΩ Each 1
3. Ammeter (0-10) mA, 1No
4. Bread board 1No
5. Connecting wires As required
6. DRB (0-10)KΩ 1No
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TABULATION:
Resistance (RL) Current I(mA) Power =I2RL
PROCEDURE:
1. Connections are given as per the circuit diagram.
2. By giving various values of the resistance in DRB, note the ammeter Reading.
3. Calculate the power and plot the power Vs resistance graph.
4. Note the maximum power point corresponding resistance from the graph.
RESULT:
Thus the value of unknown resistance in which the maximum power is transferred to the
load was found.
Theoretical load resistance =
Practical load resistance =
Maximum power =
B) VERIFICATION OF RECIPROCITY THEOREM
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AIM:
To verify Reciprocity theorem and also to determine the current flow through the load
resistance.
APPARATUS REQUIRED:
THEORY:
Reciprocity theorem
In a linear, bilateral network a voltage source V volt in a branch gives rise to a current I, in
another branch. If V is applied in the second branch the current in the first branch will be I. This
V/I are called transfer impedance or resistance. On changing the voltage source from 1 to branch 2,
the current in branch 2 appears in branch 1.
CIRCUIT DIAGRAM:
S.No. Name of the apparatus Range Quantity
1. Regulated Power supply (0-30V) 1No
2. Resistor 100Ω,470Ω,
820Ω, 100Ω
Each 1
3. Ammeter (0-30) mA, 1No
4. Bread board 1No
5. Connecting wires As required
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TABULATION:
Practical value :( circuit -I)
V(volt)
I(mA)
Z=V/I
PRACTICAL VALUE :( CIRCUIT -I)
V(volt)
I(mA)
Z=V/I
PROCEDURE:
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1. Connect the circuit as per the circuit diagram.
2. Switch on the supply and note down the corresponding ammeter readings.
3. Find ratio of input voltage to output current.
4. Interchange the position of the ammeter and power supply. Note down the Corresponding
ammeter readings
5. Verify the reciprocity theorem by equating the voltage to current ratio.
RESULT:
Thus the reciprocity theorem was verified.
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EXP. No.12 DETERMINATION OF RESONANCE FREQUENCY OF SERIES &
PARALLEL RLC CIRCUITS
AIM:
To obtain the resonance frequency of the given RLC series electrical network.
FORMULA USED:
Series resonance frequency F=1/ (2п √ (LC))
CIRCUIT DIAGRAM:
Series resonance:
TABULATION:
FREQUENCY
(HZ)
VR(VOLT)
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CIRCUIT DIAGRAM
Parallel resonance:
TABULATION:
FREQUENCY
(HZ)
VR(VOLT)
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Vary the frequency of the function generator from 50 Hz to 20 KHz.
3. Measure the corresponding value of voltage across the resistor R for series RLC circuit.
4. Repeat the same procedure for different values of frequency.
5. Tabulate your observation.
6. Note down the resonance frequency from the graph.
RESULT:
Thus the resonance frequency of series RLC circuit is obtained.
Practical value =
Theoretical value =
Thus the resonance frequency of Parallel RLC circuit is obtained.
Practical value =
Theoretical value =
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EXP. No.13 TRANSIENT ANALYSIS OF RL AND RC CIRCUITS
AIM:
To construct RL & RC transient circuit and to draw the transient curves.
APPARATUS REQUIRED:
THEORY:
Electrical devices are controlled by switches which are closed to connect supply to the
device, or opened in order to disconnect the supply to the device. The switching operation will
change the current and voltage in the device. The purely resistive devices will allow instantaneous
change in current and voltage.
An inductive device will not allow sudden change in current and capacitance device will
not allow sudden change in voltage. Hence when switching operation is performed in inductive
and capacitive devices, the current & voltage in device will take a certain time to change from pre
switching value to steady state value after switching. This phenomenon is known as transient. The
study of switching condition in the circuit is called transient analysis.The state of the circuit from
instant of switching to attainment of steady state is called transient state. The time duration from
the instant of switching till the steady state is called transient period. The current & voltage of
circuit elements during transient period is called transient response.
FORMULA:
S.No Name of the apparatus Range Type Quantity
1. Regulated Power supply (0-30V) DC 1No
2. Voltmeter (0-10)V MC 1No
3. Ammeter (0-30) mA, MC 1No
4. Resistor 10 K Ω, 3No
5. Capacitor 1000 μ F 1No
6. Bread board
7. Connecting wires
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Time constant of RC circuit = RC
PROCEDURE:
Connections are made as per the circuit diagram.
Before switching ON the power supply the switch S should be in off position
Now switch ON the power supply and change the switch to ON position
The voltage is gradually increased and note down the reading of ammeter and voltmeter for
each time duration in RC.In RL circuit measure the Ammeter reading.
Tabulate the readings and draw the graph of Vc(t)Vs t
CIRCUIT DIAGRAM:
RL CIRCUIT:
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TABULATION:
S.No. TIME (msec) CHARGING
CURRENT (I) A
DISCHARGING
CURRENT (I) A
MODEL GRAPH:
CIRCUIT DIAGRAM:
RC CIRCUIT:
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MODEL GRAPH:
CHARGING DISCHARGING
TABULATION:
CHARGING:
S.No. TIME
(msec)
VOLTAGE
ACROSS ‘C’(volts)
CURRENT
THROUGH‘C’ (mA)
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TABULATION:
DISCHARGING:
S.No. TIME (msec) VOLTAGE
ACROSS ‘C’(volts)
CURRENT
THROUGH‘C’ (mA)
RESULT:
Thus the transient response of RL & RC circuit for DC input was verified.
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EXP. No.14 Study the V-I Characteristics of LED
AIM:- A study of V-I characteristics of light emitting diode (LED).
APPARATUS REQUIRED:
CIRCUIT DIAGRAM:-
Theory: -
A Light Emitting Diode (LED) is a semiconductor diode mode by creation of junction of n type
and p type material. Thus the principle of LED action works precisely the same way that we
described the creation of permanent light radiation. Alternatively w can say that the external
energy provided by V excites electrons at the conduction band to the valence band and recombine
with hole. The net result is the light radiation.
S.No Name of the apparatus Range Type Quantity
1. Regulated Power supply (0-30V) DC 1No
2. Voltmeter (0-10)V MC 1No
3. Ammeter (0-50) mA, MC 1No
4. LED 3V 1No
5. Rheostat
- - 1No
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Fig. 1. Working Principle of LED
It consists of an encapsulated chip of semiconductor diode with a suitable lens. The length of
anode terminal is greater than cathode terminal. LEDs are based on the semiconductor diode.
When the diode is forward biased (switched on), electrons are able to recombine with holes and
energy is released in the form of light. This effect is called electroluminescence and the color of
the light is determined by the energy gap of the semiconductor. The LED is usually small in area
(less than 1 mm) with integrated optical components to shape its radiation pattern and assist in
reflection.
PROCEDURE:-
Make the connections as shown in circuit diagram. Switch on the power supply.
The voltage is set at 0 V and the current through the LED shown by milliammeter is
recorded.
With the help of slider of rheostat, the voltage is increased in steps of 0.2 V.
For each setting of the voltage, corresponding current shown by the microammeter is noted.
The observatuions are recorded in table.
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TABULATION:
Forward Voltage
(Volts)
Forward Current (mA)
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
MODEL GRAPH:-
The graph is plotted, by taking forward voltage on the positive x axis and forward current on the
positive y axis
RESULT:-
1. The LED characteristics are similar to pn-junction forward characteristics.
2. The cut-in voltage (the voltage at which conduction begins) for LED is Volts.