Introduction to The
Subject
Agenda
 Aims
 Learning Outcomes
 Textbooks
 Schedule
 Course Contents
 Assessment and Grading
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Aims
 To teach fundamental principles of standard linear
integrated circuits.
 To develop a overall approach for students from
selection of integrated circuit, study its specification,
the functionality, design and practical applications.
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Learning Outcomes
The student will be able to:
 Understand the characteristics of Operational amplifier.
 Understand the basic operational amplifier circuits and its
applications.
 Understand the different types of active filters, and its applications.
 Understand the different types of oscillators and its applications.
 Understand the different types of regulators.
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Textbooks
References:
 Thomas L. Floyd “Electronic devices”, prentice hall tenth edition, 2018.
 Neil Storey, “ELECTRONICS A systems approach”, Sixth Edition, 2017.
 Robert L. Boylestad, Louis Nashelsky “Electronic Devices and Circuit Theory”,
Eleventh Edition, 2013.
 Earl D. Gates “INTRODUCTION TO ELECTRONICS”, FIFTH EDITION, 2007.
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Schedule
Wednesday
Time
11:30 AM - 12:30 PM
Gentlemen
Room: Class 50
Time
11:30 AM - 12:30 PM
Ladies
Room: Class 50
Mr. Mohammed Alkhair
mohamedalkhair@iua.edu.sd
mohammed_alkhair2022@yahoo.com
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Course Contents
 The Operational Amplifier: Introduction to Operational Amplifiers,
Op-Amp Input Modes and Parameters, Negative Feedback, Op-Amps
with Negative Feedback, Effects of Negative Feedback on Op-Amp
Impedances.
 Basic OP-AMP Circuits: Comparators, Summing Amplifiers,
Integrators and Differentiators
 Special Purpose OP-AMP Circuits: Instrumentation Amplifiers,
Converters.
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Course Contents
 Active Filters: Basic Filter Responses, Filter Response Characteristics,
Active Low-Pass Filters, Active High-Pass Filters Active Band-Pass
Filters, Active Band-Stop Filters.
 Oscillators: The Oscillator, Feedback Oscillators, Oscillators with RC
Feedback Circuits, Oscillators with LC Feedback Circuits.
 Voltage Regulators: Voltage Regulation, Basic Linear Series Regulators,
Basic Linear Shunt Regulators, Basic Switching Regulators, Integrated
Circuit Voltage Regulators.
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Assessment and Grading
Grading
 50% Final Exam
 30% Midterm Exam
 10% Home works/ Laboratory
 10% Mini Project Hardware/Software
Warnings
 Copying assignment/quiz/exam is prohibited.
 Delay of submission influences on marks.
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Lecture 1
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Operational Amplifier
 Invented by Karl D. Swartzel Jr. in 1941.
 The operational amplifier concept originated around 1947.
 The first commercial op-amps used vacuum tubes, but it
was not until the introduction of the integrated circuit did
the op-amp start to fulfill its true potential.
 In 1964, the first integrated circuit op-amp, designated the
Figure 1 Vacuum tube
OP-AMP (1953)
702, was developed by Fairchild Semiconductor.
 This was later followed by the 709 and eventually the 741,
which has become an industry standard.
Figure 2 A typical
operational amplifier.
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Operational Amplifier
INTRODUCTION TO OPERATIONAL AMPLIFIERS
 The op amp is an electronic device consisting of a complex
arrangement of resistors, transistors, capacitors, and diodes.
 Early operational amplifiers (op-amps) were used primarily to perform
mathematical operations such as addition, subtraction, integration, and
differentiation; thus the term operational.
 These early devices were constructed with vacuum tubes and worked
with high voltages.
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Operational Amplifier
 Today’s op-amps are linear integrated circuits (ICs) that use
relatively low dc supply voltages and are reliable and inexpensive.
 The operational amplifier (op-amp) has two input terminals, the
inverting (-) input and the non-inverting (+) input, and one output
terminal.
 Most op-amps operate with two dc supply voltages, one positive
and the other negative, although some have a single dc supply.
 Usually these dc voltage terminals are left off the schematic symbol
for simplicity but are understood to be there.
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Operational Amplifier
 Op-amps are commercially available in integrated circuit packages in several forms.
 A typical one is the eight-pin dual in-line package (or DIP), shown in Figure 3(a).
Pin or terminal 8 is unused, and terminals 1 and 5 are of little concern to us.
 The five important terminals are:
1. The inverting input, pin 2.
2. The non-inverting input, pin 3.
3. The output, pin 6.
4. The positive power supply V +, pin 7.
5. The negative power supply V −, pin 4
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Operational Amplifier
(b)
(a)
Figure 3 A typical op amp:
(a) pin configuration, (b) circuit symbol.
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Operational Amplifier
Table 1 Typical ranges for op amp parameters
Parameters
Typical range
Ideal values
Open-loop gain, 𝑨
105 to 108
∞
Input resistance, 𝑹𝒊
106 to 1013 Ω
∞Ω
Output resistance, 𝑹𝒐
10 to 100 Ω
0Ω
Supply voltage, 𝑽𝒄𝒄
5 to 24 V
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Operational Amplifier
The Ideal Op-Amp
 The ideal op-amp has infinite voltage gain and infinite bandwidth.
 Also, it has an infinite input impedance (open) so that it does not
load the driving source.
 Finally, it has a zero output impedance.
 The input voltage, Vin, appears between the two input terminals,
and the output voltage is AvVin , as indicated by the internal
voltage source symbol.
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Operational Amplifier
Figure 4 Basic op-amp representations.
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Operational Amplifier
The Practical Op-Amp
 The ideal device can never be made.
 Any device has limitations, and the IC op-amp is no exception.
 Op-amps have both voltage and current limitations.
 Peak-to-peak output voltage, for example, is usually limited to
slightly less than the two supply voltages.
 Output current is also limited by internal restrictions such as
power dissipation and component ratings.
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Operational Amplifier
 Characteristics of a practical op-amp are very high voltage gain, very
high input impedance, and very low output impedance.
 Another practical consideration is that there is always noise generated
within the op-amp.
 Noise is an undesired signal that affects the quality of a desired signal.
 Today, circuit designers are using smaller voltages that require high
accuracy, so low-noise components are in greater demand.
 All circuits generate noise; op-amps are no exception, but the amount
can be minimized.
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Operational Amplifier
Internal Block Diagram of an Op-Amp
 A typical op-amp is made up of three types of amplifier
circuits: a differential amplifier, a voltage amplifier, and a
push-pull amplifier.
 The differential amplifier is the input stage for the op-amp.
 It provides amplification of the difference voltage between the
two inputs.
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Operational Amplifier
 The second stage is usually a class A amplifier that provides
additional gain.
 Some op-amps may have more than one voltage amplifier stage.
 A push-pull class B amplifier is typically used for the output stage.
 The term differential comes from the amplifier’s ability to amplify
the difference of two input signals applied to its inputs.
 Only the difference in the two signals is amplified; if there is no
difference, the output is zero.
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Operational Amplifier
Figure 5 Basic internal
arrangement of an op-amp.
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Operational Amplifier
Review Questions:
1. What are the connections to a basic op-amp?
2. Describe some of the characteristics of a practical op-amp.
3. List the amplifier stages in a typical op-amp.
4. What does a differential amplifier amplify?
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Operational Amplifier
OP-AMP INPUT MODES AND PARAMETERS
Input Signal Modes
 The input signal modes are determined by the
differential amplifier input stage of the op-amp.
Differential Mode
 In the Single-ended mode , either one signal is
applied to an input with the other input grounded or
two opposite-polarity signals are applied to the inputs.
Figure 6 Single-ended
differential mode.
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Operational Amplifier
 In the double-ended differential mode, two
opposite-polarity (out-of-phase) signals are
applied to the inputs.
 The amplified difference between the two
inputs appears on the output.
 Equivalently, the double-ended differential
mode can be represented by a single
source connected between the two inputs.
Figure 7 Double-ended differential mode.
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Operational Amplifier
Common Mode
 In the common mode, two signal voltages of the same phase,
frequency, and amplitude are applied to the two inputs.
 When equal input signals are applied to both inputs,
they tend to cancel, resulting in a zero output voltage.
 This action is called common-mode rejection.
 Common-mode rejection means that this unwanted
signal will not appear on the output and distort the
desired signal.
Figure 8 Common-mode operation.
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Operational Amplifier
Op-Amp Parameters
Common-Mode Rejection Ratio
 Desired signals can appear on only one input or with opposite
polarities on both input lines.
 Unwanted signals (noise) appearing with the same polarity on both
input lines are essentially cancelled by the op-amp and do not appear
on the output.
 The measure of an amplifier’s ability to reject common-mode signals
is a parameter called the CMRR (common-mode rejection ratio).
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Operational Amplifier
 Ideally, an op-amp provides a very high gain for differentialmode signals and zero gain for common-mode signals.
 Practical op-amps, however, do exhibit a very small commonmode gain (usually much less than 1), while providing a high
open-loop differential voltage gain (usually several thousand).
 The higher the open-loop gain with respect to the commonmode gain, the better the performance of the op-amp in terms
of rejection of common-mode signals.
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Operational Amplifier
 This suggests that a good measure of the op-amp’s
performance in rejecting unwanted common-mode signals is
the ratio of the open-loop differential voltage gain, Aol, to the
common-mode gain, Acm.
 This ratio is the common-mode rejection ratio, CMRR.
 The higher the CMRR, the better.
 A very high value of CMRR means that the open-loop gain, Aol ,
is high and the common-mode gain, Acm, is low.
 The CMRR is often expressed in decibels (dB) as
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Operational Amplifier
 The open-loop voltage gain, Aol, of an op-amp is the internal
voltage gain of the device and represents the ratio of output
voltage to input voltage when there are no external components.
 The open-loop voltage gain is set entirely by the internal design.
 Open-loop voltage gain can range up to 200,000 (106 dB) and is
not a well-controlled parameter.
 Datasheets often refer to the open-loop voltage gain as the largesignal voltage gain.
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Operational Amplifier
 A CMRR of 100,000, for example, means that the desired input
signal (differential) is amplified 100,000 times more than the
unwanted noise (common-mode).
 If the amplitudes of the differential input signal and the
common-mode noise are equal, the desired signal will appear
on the output 100,000 times greater in amplitude than the noise.
 Thus, the noise or interference has been essentially eliminated.
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Operational Amplifier
Example 1:
A certain op-amp has an open-loop differential voltage gain of
100,000 and a common-mode gain of 0.2. Determine the CMRR and
express it in decibels.
Solution:
CMRR = 500000 = 114 dB
Related Problem:
Determine the CMRR and express it in dB for an op-amp with an open-
loop differential voltage gain of 85,000 and a common-mode gain of 0.25.
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Operational Amplifier
Maximum Output Voltage Swing (VO(p-p))
 With no input signal, the output of an op-amp is ideally 0 V.
This is called the quiescent output voltage.
 When an input signal is applied, the ideal limits of the peak-topeak output signal are ±Vcc.
 In practice, however, this ideal can be approached but never
reached.
 VO(p-p) varies with the load connected to the op-amp and
increases directly with load resistance.
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Operational Amplifier
Input Offset Voltage
 The ideal op-amp produces zero volts out for zero volts in.
 In a practical op-amp, however, a small dc voltage, VOUT(error),
appears at the output when no differential input voltage is applied.
 The input offset voltage, VOS, is the differential dc voltage
required between the inputs to force the output to zero volts.
 Typical values of input offset voltage are in the range of 2 mV or
less. In the ideal case, it is 0 V.
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Operational Amplifier
Input Bias Current
 The input terminals of a bipolar differential
amplifier are the transistor bases and, therefore,
the input currents are the base currents.
 The input bias current is the dc current required
by the inputs of the amplifier to properly
operate the first stage. By definition, the input
Figure 9 Input bias current is the average
of the two op-amp input currents.
bias current is the average of both input
currents and is calculated as follows:
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Operational Amplifier
Input Impedance
 Two basic ways of specifying the input impedance of an op-amp
are the differential and the common mode.
 The differential input impedance is the total resistance between
the inverting and the non-inverting inputs.
 Differential impedance is measured by determining the change
in bias current for a given change in differential input voltage.
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Operational Amplifier
 The common-mode input impedance is the resistance between
each input and ground and is measured by determining the change
in bias current for a given change in common-mode input voltage.
Figure 10 Op-amp input impedance
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Operational Amplifier
Input Offset Current
 Ideally, the two input bias currents are equal, and thus their difference
is zero.
 In a practical op-amp, however, the bias currents are not exactly equal.
 The input offset current, IOS, is the difference of the input bias currents,
expressed as an absolute value.
 Actual magnitudes of offset current are usually at least an order of
magnitude (ten times) less than the bias current.
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Operational Amplifier
 In many applications, the offset current can be neglected.
 However, high-gain, high-input impedance amplifiers should
have as little IOS as possible because the difference in currents
through large input resistances develops a substantial offset
voltage.
Figure 11 Effect of
input offset current.
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Operational Amplifier
 The offset voltage developed by the input offset current is
 The error created by IOS is amplified by the gain Av of the op-amp
and appears in the output as
Output Impedance
Figure 12 Op-amp
output impedance.
 The output impedance is the resistance viewed
from the output terminal of the op-amp,
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Operational Amplifier
Slew Rate
 The maximum rate of change of the output voltage in response
to a step input voltage is the slew rate of an op-amp.
 The slew rate is dependent upon the high-frequency response of
the amplifier stages within the op-amp.
 For a step input, the slope on the output is inversely proportional
to the upper critical frequency.
 Slope increases as upper critical frequency decreases.
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Operational Amplifier
Figure 13 Slew-rate measurement
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Operational Amplifier
 The width of the input pulse must be sufficient to allow the
output to “slew” from its lower limit to its upper limit.
 The unit of slew rate is volts per microsecond (V/𝜇s).
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Operational Amplifier
Example 2:
The output voltage of a certain op-amp appears as
shown in Figure 14 in response to a step input.
Determine the slew rate.
Solution:
Slew rate = 18 V/𝜇s
Related Problem:
When a pulse is applied to an op-amp, the output voltage goes
from -8 V to +7 V in 0.75 𝜇s. What is the slew rate?
Figure 14
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Operational Amplifier
Review Questions:
1. Distinguish between single-ended and double-ended differential mode.
2. Define common-mode rejection.
3. For a given value of open-loop differential gain, does a higher
common-mode gain result in a higher or lower CMRR?
4. List five op-amp parameters.
5. How is slew rate measured?
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Operational Amplifier
NEGATIVE FEEDBACK
 Negative feedback is one of the most useful concepts in
electronics, particularly in op-amp applications.
 Negative feedback is the process whereby a portion of the
output voltage of an amplifier is returned to the input with a
phase angle that opposes (or subtracts from) the input signal.
 The inverting input effectively makes the feedback signal 180°
out of phase with the input signal.
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Operational Amplifier
Figure 15 Illustration
of negative feedback.
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Operational Amplifier
Why Use Negative Feedback?
 The inherent open-loop voltage gain of a typical op-amp is very high,
small input voltage drives the op-amp into its saturated output states. In
fact, even the input offset voltage of the op-amp can drive it into saturation.
 For example, assume VIN = 1 mV and Aol =100,000.
 Then, VINAol = (1 mV)(100,000) = 100 V.
 Since the output level of an op-amp can never reach 100 V, it is driven
deep into saturation and the output is limited to its maximum output levels,
for both a positive and a negative input voltage of 1 mV.
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Operational Amplifier
 The usefulness of an op-amp operated without negative
feedback is generally limited to comparator applications.
 With negative feedback, the closed loop voltage gain (Acl) can
be reduced and controlled so that the op-amp can function as a
linear amplifier.
 In addition to providing a controlled, stable voltage gain,
negative feedback also provides for control of the input and
output impedances and amplifier bandwidth.
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Operational Amplifier
Figure 16 Without negative feedback, a
small input voltage drives the op-amp to
its output limits and it becomes nonlinear.
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Operational Amplifier
Table 2 summarizes the general effects of negative feedback on op-amp performance
VOLTAGE GAIN
INPUT Z
OUTPUT Z
BANDWIDTH
Relatively low
Relatively narrow
Without
Aol is too high for
negative
linear amplifier
(because the gain is so
Feedback
application
high)
With
Aol is set to desired
Can be increased or Can be reduced to a
negative
value by the
reduced to desired
Feedback
feedback circuit
value depending on
Relatively high
Significantly wider
desired value
type of circuit
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Operational Amplifier
Review Questions:
1. What are the benefits of negative feedback in an op-amp circuit?
2. Why is it generally necessary to reduce the gain of an op-amp
from its open-loop value?
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Operational Amplifier
Problems:
1. Compare a practical op-amp to an ideal op-amp.
2. Two IC op-amps are available to you. Their characteristics
are listed below. Choose the one you think is more desirable.
Op-amp 1: Zin = 5 MΩ, Zout = 100 Ω, Aol = 50,000
Op-amp 2: Zin = 10 MΩ, Zout = 75 Ω, Aol = 150,000
3. The open-loop gain of a certain op-amp is 175,000. Its
common-mode gain is 0.18. Determine the CMRR in decibels.
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Operational Amplifier
4. An op-amp datasheet specifies a CMRR of 300,000 and an
Aol of 90,000. What is the common mode gain?
5. Determine the bias current, IBIAS, given that the input currents
to an op-amp are 8.3 𝜇A and 7.9 𝜇A.
6. Distinguish between input bias current and input offset
current, and then calculate the input offset current in Problem 5.
7. Figure 17 shows the output voltage of an op-amp in response
to a step input. What is the slew rate?
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Operational Amplifier
8. How long does it take the output voltage of an op-amp to go from
-10 V to +10 V if the slew rate is 0.5 V/𝜇S?
Figure 17
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Education is what remains after one
has forgotten everything he learned
in school.
— Albert Einstein
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FOR
LISTENING
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