Department of ECE Electronic Circuit Analysis Laboratory Vardhaman College of Engineering, Hyderabad Page 1 1. INTRODUCTION 1.1 PURPOSE OF THE LAB: This manual has been prepared for use in the course Electronics & Communication Engineering, Electronic Circuits Laboratory. The laboratory exercises are designed in such a way as to reinforce the concepts taught in the lectures. Before performing the experiments, the students must be aware of the basic safety rules for minimizing any potential dangers. The specific objective of each experiment should be kept in mind throughout the laboratory session. The conclusions based on the experiments and other observed phenomena must be clearly discussed in the laboratory report. 1.2 PURPOSE OF THE PRELAB: In each lab, you are given prelab questions. These are intended to help you prepare for the lab. You should write your response in this manual. These questions are not handed in, and they are not graded. If you do not understand a prelab question, be sure to ask your Instructor. 2. CIRCUIT ANALYSIS USING PSPICE PURPOSE 1. To learn the basic features of PSpice. 2. To use PSpice for the following: i) Analysis by using Schematic Editor. ii) Analysis by using Circuit File Editor. INTRODUCTION TO SPICE The rapid change in the field of electrical engineering is paralleled by programs that use the computers increased capabilities in the solution of both traditional and novel problems. With the availability of tools for computer-aided circuit analysis, circuits of great complexity can be designed and analyzed within a shorter time and with less effort compared to the traditional methods. PSpice is a member of the SPICE (Simulation Program with Integrated Circuit Emphasis) family of circuit simulators. In the following exercises you will use PSpice to solve some circuits and to determine the quantities of interest. Simulation Program with Integrated Circuit Emphasis (SPICE) SPICE is a computer simulation and modeling program used by engineers to mathematically predict the behavior of electronic circuits. Developed at the University of California at Berkeley, SPICE can be used to simulate circuits of almost all complexities. However, SPICE is generally used to predict the behavior of low to mid frequency (DC to around 100MHz) circuits. SPICE has the ability to simulate components ranging from the most basic passive elements such as resistors and capacitors to sophisticated semiconductor devices such as MESFETs and MOSFETs. Using these intrinsic components as the basic building blocks for larger models, designers and chip manufacturers have been able to define a truly vast and diverse number of SPICE models. Most commercially available simulators include more than 15,000 different components.
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Department of ECE Electronic Circuit Analysis Laboratory
Vardhaman College of Engineering, Hyderabad Page 1
1. INTRODUCTION
1.1 PURPOSE OF THE LAB:
This manual has been prepared for use in the course Electronics & Communication
Engineering, Electronic Circuits Laboratory. The laboratory exercises are designed in such a
way as to reinforce the concepts taught in the lectures. Before performing the experiments,
the students must be aware of the basic safety rules for minimizing any potential dangers.
The specific objective of each experiment should be kept in mind throughout the laboratory
session. The conclusions based on the experiments and other observed phenomena must be
clearly discussed in the laboratory report.
1.2 PURPOSE OF THE PRELAB:
In each lab, you are given prelab questions. These are intended to help you prepare
for the lab. You should write your response in this manual. These questions are not handed
in, and they are not graded. If you do not understand a prelab question, be sure to ask your
Instructor.
2. CIRCUIT ANALYSIS USING PSPICE
PURPOSE
1. To learn the basic features of PSpice.
2. To use PSpice for the following:
i) Analysis by using Schematic Editor.
ii) Analysis by using Circuit File Editor.
INTRODUCTION TO SPICE
The rapid change in the field of electrical engineering is paralleled by programs that
use the computers increased capabilities in the solution of both traditional and novel
problems. With the availability of tools for computer-aided circuit analysis, circuits of great
complexity can be designed and analyzed within a shorter time and with less effort
compared to the traditional methods.
PSpice is a member of the SPICE (Simulation Program with Integrated Circuit
Emphasis) family of circuit simulators. In the following exercises you will use PSpice to solve
some circuits and to determine the quantities of interest.
Simulation Program with Integrated Circuit Emphasis (SPICE)
SPICE is a computer simulation and modeling program used by engineers to
mathematically predict the behavior of electronic circuits.
Developed at the University of California at Berkeley, SPICE can be used to simulate
circuits of almost all complexities. However, SPICE is generally used to predict the behavior
of low to mid frequency (DC to around 100MHz) circuits.
SPICE has the ability to simulate components ranging from the most basic passive
elements such as resistors and capacitors to sophisticated semiconductor devices such as
MESFETs and MOSFETs. Using these intrinsic components as the basic building blocks for
larger models, designers and chip manufacturers have been able to define a truly vast and
diverse number of SPICE models. Most commercially available simulators include more than
15,000 different components.
Department of ECE Electronic Circuit Analysis Laboratory
Vardhaman College of Engineering, Hyderabad Page 2
A circuit must be presented to SPICE in the form of a netlist. The netlist is a text
description of all circuit elements such as transistors and capacitors, and their corresponding
connections. Modern schematic capture and simulation tools such as Multisim allow users
to draw circuit schematics in a user-friendly environment, and automatically translate the
circuit diagrams into netlists. Both netlist and corresponding circuit schematic are presented
here in this manual, and some are left to the students to write on their own for practice.
Types Of Spice
The commercially supported versions of SPICE2 can be divided into two types: mainframe
versions and PC–based versions.
The mainframe versions are:
HSPICE, RAD-SPICE(Meta-Software)
IG-SPICE(A.B.Associates)
Precise(Electronic Engineering Software)
PSpice(Microsim)
AccuSim(Mentor Graphics)
Cadence-SPICE(Cadence Design)
SPICE-Plus(valid Logic)
The PC-versions are
AllSpice(Acotech)
IS-SPICE(Intusoft)
Z-SPICE(Z-Tech)
SPICE-Plus(Analog Design Tools)
DSPICE(Daisy Systems)
PSpice(Microsim)
Types of Analysis
Pspice allows various types of analysis. Each analysis is invoked by including its
command statement.
The types of analysis and their corresponding. (dot) commands are described below:
DC Analysis is used for circuits with time-invariant sources(e.g., steady-state dc
sources).
DC Analysis Commands:
• DC sweep of an input voltage/current source, a model parameter, or temperature
over a range of values (.DC)
• DC operating point to obtain all node voltages (.OP)
• Small-signal transfer function with small-signal gain, input resistance, and output
resistance (Thevenin’s equivalent) (.TF)
• DC small-signal sensitivities (.SENS)
Transient Analysis is used for circuits with time-variant sources (e.g., ac sources
and switched dc sources).
Transient Analysis Commands:
• Circuit behavior in response to time varying sources (.TRAN)
• DC and Fourier components of the transient analysis results (.FOUR)
AC Analysis is used for small-signal analysis of circuits with sources of variable
frequencies.
AC Analysis Commands:
• Circuit response over a range of source frequencies (.AC)
• Noise generation at an output node for every frequency (.NOISE)
Department of ECE Electronic Circuit Analysis Laboratory
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Limitation Of Spice
As a circuit simulator, Pspice has the following limitations:
1. The student version of Pspice is restricted to circuits with 10 transistors only.
2. The program is not interactive; that is, the circuit cannot be analyzed for various
component values without editing the program statements.
3. Pspice does not support an iterative method of solution. If the elements of a circuit
are specified, the output can be predicted. On the other hand, if the output is
specified, Pspice cannot be used to synthesize the circuit elements.
4. The input impedance cannot be determined directly.
5. The PC version needs 512kilobytes of memory (RAM) to run.
6. Distortion analysis is not available in Pspice.
7. The output impedance of a circuit cannot be printed or plotted directly.
Circuit Descriptions
A circuit is described to a computer by using a file called the circuit file, which is
normally typed from a keyboard. The circuit file contains the circuit details of components
and elements, the information about the sources, and the commands for what to calculate
and what to provide as output.
The circuit file is the input to the SPICE program, which after executing the
commands, produces the results in another file called the output file.
A circuit must be specified in terms of element names, element values, nodes,
variable parameters, and sources.
The description and analysis of a circuit require specifications as follows:
• Element values
• Nodes
• Circuit elements
• Element models
• Sources
• Types of analysis
• Output variables
• PSpice output commands
• Format of circuit files
• Format of output files
Element Values: The element values are written in standard floating point notation with
optional scale and unit suffixes. Some values without suffixes that are allowable in PSpice
are
5 .5 5.0 5E+3 5.0E+3 5.E+3
There are two types of suffixes: the scale suffix and the unit suffix. The scale suffix
multiplies the number that it follows. The scale suffixes recognized by PSpice are
F = 1E-15
P = 1E-12
N = 1E-9
U = 1E-6
M = 1E-3
MIL = 25.4E-6
K = 1E3
MEG = 1E6
G = 1E9
T = 1E12
Department of ECE Electronic Circuit Analysis Laboratory
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The unit suffixes that are normally used are
V=volt
A=amp
HZ=hertz
OHM=ohm(Ω)
H=henry
F=farad
DEG=degree
The first suffix always the scale suffix and the unit suffix follows the scale suffix. In the
absence of a scale suffix, the first suffix may be a unit suffix, provided it is not symbol of a
scale suffix.
Nodes: The location of an element is identified by the node numbers. Each element is
connected between two nodes. Node numbers are assigned to the circuit. Node 0 is
predefined as the ground. All nodes must be connected to at least two elements and should,
therefore, appear at least twice. Node numbers must be integers from 0 to 9999 for SPICE,
but need not be sequential.
Circuit Elements: Circuit elements are identified by names. A name must start with a
letter symbol corresponding to the element, but after it can contain either letters or
numbers. Names can be up to 8 characters long for SPICE2 and up to 131 characters long
The practical circuit of CE amplifier is shown in the figure. It consists of different
circuit components. The functions of these components are as follows:
1. Biasing Circuit: The resistances R1, R2 and RE form the voltage divider biasing
circuit for the CE amplifier. It sets the proper operating point for the CE amplifier.
2. Input capacitor C1: This capacitor couples the signal to the transistor. It blocks
any dc component present in the signal and passes only ac signal for amplification.
Because of this, biasing conditions are maintained constant.
3. Emitter Bypass Capacitor CE: An emitter bypass capacitor CE is connected in
parallel with the emitter resistance, RE to provide a low reactance path to the
amplified ac signal. If it is not inserted, the amplified ac signal passing through RE
will cause a voltage drop across it. This will reduce the output voltage, reducing the
gain of the amplifier.
4. Output Coupling Capacitor C2: The coupling capacitor C2 couples the output of
the amplifier to the load or to the next stage of the amplifier. It blocks dc and passes
only ac part of the amplified signal.
Operation: When positive half of the signal is applied, the voltage between base and
emitter (Vbe) is increased because it is already positive with respect to ground. So forward
bias is increased i.e., the base current is increased. Due to transistor action, the collector current IC is increased β times. When this current flows through RC, the drop IC RC increases
considerably. As a consequence of this, the voltage between collector and emitter (Vce)
decreases. In this way, amplified voltage appears across RC. Therefore the positive going
input signal appears as a negative going output signal i.e., there is a phase shift of 180°
between the input and output.
Department of ECE Electronic Circuit Analysis Laboratory
Vardhaman College of Engineering, Hyderabad Page 11
Procedure:
1. Schematic:
i) Select the components from the symbol library and place it on the
schematic window.
ii) The selected symbol is displayed on the screen in red. Move the symbol to
the desired location using the mouse.
iii) You can change the view of most symbols by performing the following
operations: rotate, mirror and flip.
iv) Wires and junctions are used to wire together parts and indicate electrical
connections.
v) To draw a wire, select the Wire menu command, Move the cursor to the
wire starting position and click the left mouse button or press Enter. Now
you can move the other end of wire to the desired location.
vi) The junction symbol (a large dot) indicates an electrical connection
between wires or between a wire and a part pin.
vii) Most parts (components) require that you specify the following set of
attributes: reference name, value or model name, and optional
parameters.
viii) You can also change the attributes by double-clicking on a part on the
schematic.
ix) Once circuit construction is completed; the analysis is to be performed.
x) To simulate a circuit, select the Analysis|Run Simulation menu command
from the Schematic.
xi) If there are any errors during the simulation, the simulator writes any
applicable error messages to the simulation output file.
xii) Three different modes of circuit analysis: DC, AC (frequency response)
and transient.
xiii) Before simulation, we have to do the analysis setup.
xiv) Once analysis setup is over, then perform Run Simulation.
xv) From the analysis note down the readings, plot the graph, do the
calculations.
2. Circuit File:
i) The SPICE circuit file (default filename extension ".CIR") is the input file
for the simulator program.
ii) This is a text file, which contains the circuit netlist, simulation command
and device model statements.
iii) Write the circuit file for the given schematic assuming the node numbers.
Save the circuit file.
iv) To simulate the circuit file, select the Analysis|Run Simulation menu
command from the circuit file menu.
v) If there are any errors during the simulation, the simulator writes any
applicable error messages to the simulation output file.
vi) Three different modes of circuit analysis: DC, AC (frequency response)
and transient.
vii) Before simulation, we have to do the analysis setup.
viii) Once analysis setup is over, then perform Run Simulation.
ix) From the analysis note down the readings, plot the graph, do the
calculations.
Department of ECE Electronic Circuit Analysis Laboratory
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Observations/Graphs:
i) Transient Response:
ii) Frequency Response:
(Absolute gain Vs Frequency):
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(Gain in dB Vs Frequency):
Inference:
1. From the transient analysis the phase relationship between input and output voltage
signals is ___________ degrees.
2. From the frequency response curve the following results are calculated:
S. No. Parameter Value
1 Max. Absolute Gain
2 Max. Gain in dB
3 3dB Gain
4 Lower Cutoff Frequency
5 Upper Cutoff Frequency
6 Bandwidth
Department of ECE Electronic Circuit Analysis Laboratory
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Criticism:
1. Why the CE amplifier provides a phase reversal?
2. In the dc equivalent circuit of an amplifier, how are capacitors treated?
3. What is the effect of bypass capacitor on frequency response?
4. Define lower and upper cutoff frequencies for an amplifier.
5. State the reason for fall in gain at low and high frequencies.
6. What is meant by unity gain frequency?
7. Define Bel and Decibel.
8. What do we represent gain in decibels?
9. Why do you plot the frequency response curve on a semi-log paper?
Department of ECE Electronic Circuit Analysis Laboratory
Vardhaman College of Engineering, Hyderabad Page 15
WORKSPACE
Department of ECE Electronic Circuit Analysis Laboratory
Vardhaman College of Engineering, Hyderabad Page 16
Prelab:
1. Study the purpose of using multistage amplifiers.
2. Learn the different types of coupling methods.
3. Study the effect of cascading on Bandwidth.
4. Identify all the formulae you will need in this Lab.
5. Study the procedure of using Spice tool (Schematic & Circuit File).
Objective:
1. To simulate the Two Stage RC Coupled Amplifier in PSpice and study the transient
and frequency response.
2. To determine the phase relationship between the input and output voltages by
performing the transient analysis.
3. To determine the maximum gain, 3dB gain, lower and upper cutoff frequencies and
bandwidth of Two Stage RC Coupled Amplifier by performing the AC analysis.
4. To determine the effect of cascading on gain and bandwidth.
Software Tool:
EdwinXP / Topspice / Multisim / Microsim / or any other equivalent tool.
Circuit Diagram:
Circuit File:
Left to the student to write on his/her own
PART – I EXPERIMENT NO. – 2
TWO STAGE RC COUPLED AMPLIFIER
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Theory:
An amplifier is the basic building block of most electronic systems. Just as one brick
does not make a house, a single-stage amplifier is not sufficient to build a practical
electronic system. The gain of the single stage is not sufficient for practical applications. The
voltage level of a signal can be raised to the desired level if we use more than one stage.
When a number of amplifier stages are used in succession (one after the other) it is called a
multistage amplifier or a cascade amplifier. Much higher gains can be obtained from the
multi-stage amplifiers.
In a multi-stage amplifier, the output of one stage makes the input of the next
stage. We must use a suitable coupling network between two stages so that a minimum loss
of voltage occurs when the signal passes through this network to the next stage. Also, the
dc voltage at the output of one stage should not be permitted to go to the input of the next.
If it does, the biasing conditions of the next stage are disturbed.
Figure shows how to couple two stages of amplifiers using RC coupling scheme. This
is the most widely used method. In this scheme, the signal developed across the collector
resistor RC of the first stage is coupled to the base of the second stage through the capacitor
CC. The coupling capacitor blocks the dc voltage of the first stage from reaching the base of
the second stage. In this way, the dc biasing of the next stage is not interfered with. For
this reason, the capacitor CC is also called a blocking capacitor.
As the number of stages increases, the gain increases and the bandwidth decreases.
RC coupling scheme finds applications in almost all audio small-signal amplifiers used
in record players, tape recorders, public-address systems, radio receivers, television
receivers, etc.
Procedure: Procedure is same as that of Experiment No. 1
Observations/Graphs:
i) Transient Response:
Department of ECE Electronic Circuit Analysis Laboratory
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ii) Frequency Response:
(Gain in dB Vs Frequency)
(Comparing single stage and two stage amplifier response)
Department of ECE Electronic Circuit Analysis Laboratory
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Inference:
1. From the transient analysis, it is observed that,___________________________
The Colpitt’s Oscillator is shown in the fig. 16.1. The feedback network consisting of capacitors C1, C2 and an inductor L determines the frequency of oscillator. The frequency of Colpitt’s oscillator is
given by 1 2
1 2
1
2r
C Cf
LC Cπ+= . The condition for sustained oscillations is
2
1fe
Ch
C= .
PART – II EXPERIMENT NO. – 5(b)
COLPITT’S OSCILLATOR
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Procedure:
1. Connect the circuit on the bread board as shown in fig 16.1
2. Connect CRO at the output terminals of the circuit.
3. Note down the amplitude and frequency of the output signal.
4. This frequency will be the frequency of oscillations of Colpitt’s oscillator.
Expected Graph:
Calculations:
Frequency of oscillations, fO = 1
2 LCπ ,
where C = 1 2
1 2
C C
C C+
Observations:
Theoretical frequency of oscillations =
Practical frequency of oscillations =
Inference:
Frequency of given Colpitt’s oscillator is determined both practically and theoretically.
Criticism:
1. What is the condition for sustained oscillations in Colpitt’s oscillator?
2. In Colpitt’s oscillator, which elements provide required dc bias to the transistor?
3. In Colpitt’s oscillator, which elements determine the frequency of the output signal?
4. What are the applications of Colpitt’s oscillator?
5. What are the differences between Colpitt’s oscillator and Hartley oscillator?
VO
t
Department of ECE Electronic Circuit Analysis Laboratory
Vardhaman College of Engineering, Hyderabad Page 59
Workspace
Department of ECE Electronic Circuit Analysis Laboratory
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PreLab:
1. Study the operation and working principle of Class C Power Amplifier.
2. Study the procedure for conducting the experiment in the lab.
Objectives:
To determine the efficiency of Class C Power Amplifier.