The document discusses signal amplification using operational amplifiers (op amps). It begins with an introduction to amplifiers and their uses, then describes the experimental setup and components. The main body explains op amp theory, including that they increase signal strength using an external power source. Negative feedback is introduced to control the op amp's very high open-loop gain and produce a useful range of amplification. Kirchhoff's current law is applied to derive an expression for the closed-loop voltage gain of the feedback amplifier. The experiment involves building inverting and non-inverting op amp circuits to achieve different gains and observing input and output signals on an oscilloscope.

1. © N. B. Dodge 01/12
ENGR 2105 – Signal Amplification
1. Introduction and Goal: Amplifiers increase the power
(amplitude) of an
electrical signal. They are used in audio and video systems and
appliances.
Amplifiers are designed to amplify signals within a frequency
range. Today,
we study an operational amplifier and use it to amplify a
sinusoidal signal.
2. Equipment List: Required instruments and components are
shown below.
• Multisim
3. Experimental Theory: Amplifiers increase signal strength
(Figure 1) due
to power from an external source, unlike the passive circuit
elements that we
have studied so far. We won’t cover amplifier internals but
instead
concentrate on the fundamentals of operation.

2. 3.1 Theory of the operational amplifier: Figure 2 shows a basic
“op amp.”
3.1.1 The op amp has inverting and non-inverting inputs (─ and
+), an output, and two power inputs, +V and ─V (DC
voltages). It has no ground (or 0 V) input, but you can use
power supply ground to attach to the ground lead of the
oscilloscope probe.
3.1.2 An op amp cannot have an output larger than its power
supply voltages. If the +V DC voltage is, for example,
+15V., then the output cannot possibly exceed +15V. If the
output would have a swing of more than ±15 V or more, the
output voltage swing will be clipped (Figure 3). In practice,
clipping occurs when the output of the op amp is much less
© N. B. Dodge 01/12
than the ± supply voltage. A good rule of thumb is that the
op amp output should limited to about 60-70% of the supply

3. voltage limits.
3.1.3 The amount of amplification of an op amp is called gain.
The maximum gain of most operational amplifiers is very
large (usually > 100,000). Op amp gain can be reduced to a
useful range by “negative feedback,” which is discussed
below.
3.1.4 If op amp output is between ±0.6V, (± V = the DC power
levels), it is operating in its “linear gain region.” Thus,
amplification is constant and linear. Output is K times the
input, where K a constant, as shown in Figure 4.
3.1.5 Important op amp characteristics: (1) high input
resistance,
(~ 1 MegΩ), and (2) low output impedance (a few hundred
Ω or less).
3.1.6 With its high gain, low output resistance and high input
impedance, the op amp is easy to analyze if we assume: (1)
Input impedance is infinite (→∞), (2) output impedance →
0, (3) gain →∞.
3.2 Negative Feedback: With such high K, the op amp would

4. only be
useful to amplify only tiny inputs. To amplify larger inputs, we
can
use negative feedback to lower K.
3.2.1 In Figure 5, the input is vi(t) and the output signal is
vO(t).
The circuit resistors are Ri (input resistor), Rf (feedback
resistor), and RL (load resistor). Input voltages are ±V.
3.2.2 Using assumptions of 3.1.6: Since amplifier input
impedance is large, we assume input current is negligible: in
= 0. Since vp = 0 (ground = 0V), and since in is 0, then vn =
vp = 0. These are approximations, but they are close enough
for our analysis.
© N. B. Dodge 01/12
3.2.3 By Kirchoff’s current node law ∑����� = 0, “Node n”
(Figure 6). Then �� + �� = ��. Since in = 0, then �� + ��
= 0.
From the Figure 5, �� = (�� − ��) ��⁄ )and �� =
(�� − ��) ��⁄ . But �� = �� = 0, so that �� = �� ��⁄
and

5. �� = �� ��⁄ .
3.3 Discovery Exercise: In your worksheet, use the information
above to
develop a formula for the gain, which you will use in the
exercises
below.
4. Pre-Work: Prior to lab, watch the lecture (link on eCampus)
and complete
the worksheet.
5. Experimental Procedure:
5.1 Negative Feedback Amplifier:.
5.1.1 In Multisim, select the “UA741” op amp from the “Analog
→ OpAmps” menu.
5.1.2 For the input resistor, use a resistor of resistance Ri = 1
kΩ
5.1.3 Set up the feedback resistor for an amplification of K=10
(technically
─10). Based on the 1kΩ value of Ri, use your formula for K to
select
the feedback resistor, Rf, and connect it as shown in the video.
5.1.4 Use a 1kΩ resistor for the load resistor. (Since there is
very little
current in this circuit, your choice for load resistor does not
matter.)

6. 5.1.5 Place your ground connection and a voltage probe to
measure the
voltage across the Load Resistor.
5.1.6 Place a voltage probe to measure the voltage from the
voltage source.
© N. B. Dodge 01/12
5.1.7 Set the AC Voltage source to to 1 Vp = 0.5 Volts at 1000
Hz.
5.1.8 Start the simulation.
5.1.9 Use the “Grapher” to see the input and output AC signals.
5.1.10 If resistor selection is correct, the output should be ~ 5
Vp. Is your
output that value? Note input and output peak voltages on your
data
sheet. Calculate gain using selected resistor values. Are they
close?
5.1.11 Take a screen shot of your Multisim circuit and include it
in your
lab report.
5.1.12 Change feedback resistor for a gain of ~ 50.
5.1.13 Change the AC Voltage Source to a peak voltage of 100
mV. Start the
simulation and check the output In the grapher. Record second

7. resistor value calculated for K=50.
5.1.14 Take a screen shot of your Multisim circuit and include it
in your
lab report.
5.1.15 The op amp is an inverting amplifier in negative-
feedback mode.
Looking at the Grapher, you should see that the phase of the
output is
180 degrees from the input.
5.2 Design Exercise (Hint: Related to the activity you did in
the
Worksheet )– A Non-Inverting Amplifier: What if you need a
non-
inverting amplifier (one that does not produce an output that is
180
degrees out of phase with the input)?
5.2.1 Design a non-inverting op amp circuit with a gain of 100,
using resistors and a second op amp. You can still use the
equation that you developed for the earlier design. Note: to
preserve the condition that the op amp output voltage be no
more than about 60-70% of the power supply maximum
input voltages, the input should have a peak voltage of no

8. more than 50 mV.
5.2.2 Hints: (1) When amplifiers are cascaded (the output of the
1st op amp is fed into the input resistor of the 2nd op amp),
their gains multiplie Total Gain = (Gain from Op Amp 1) x
(Gain from Op Amp 2).
5.2.3 Hints: (2) Each negative-feedback op amp inverts the
signal.
5.2.4 After demonstrating amplifier circuit, the experiment is
complete.
5.2.5 Take a screen shot of your Multisim circuit and include
it in your lab report.
© N. B. Dodge 01/12
6. Laboratory Area Cleanup: Wash your hands!
7. Writing the Laboratory Report: In your report, do the
following:
7.1 Discuss gain characteristics of the op amp. Did your
amplification
formula work?
7.2 How did the calculated gain and actual gain compare?

9. 7.3 How accurate was the amplification in your non-inverting
circuit?
7.4 What, if any, problems did you encounter?
Please submit answers to the following questions in a Word
document as a Nurse Practitioner Student:
1. What are your strengths during this clinical rotation? (3-4
points)
1. What are your weaknesses during this clinical rotation? (2-3
points)
1. What methods do you have in place to help overcome barriers
in your clinical rotation? (3-4 point)
Answer
In clinical rotation, nurse practitioners have a set of weaknesses
and strengths. The strengths and weaknesses may vary from
skill, attitude, knowledge, and decision to detect and solve a
health problem. The practical experience makes a nurse
practitioner able to find its disabilities and develop
professionalism and create nursing skills (Karimi et al., 2017).
Strengths during Clinical Rotation
In the clinical rotations, I'm great at certain traits that are
highlighted as a strength. The strengthening factors observed
during clinical rotation are divided into three categories:
Knowledge Related Strength
Some technical based skills, such as computer skills, speaking
skills, and communication style, are improved with knowledge.
These are very important in the nursing profession. I have a
good grip on this expertise.
Personality Traits
The behavioral responses, calm nature, ability to face a stressed
situation, individual role, teamwork, hard work, and smart work
are the nurse practitioner's personality strengths. These traits

10. make a nurse's personality more potent. I have all these skills as
one of my professional strengths.
Other Skills
An organized way of working, multitasking approach, and
leadership characteristics are some other strengths. Critical
thinking is also an important strength of a nurse practitioner to
detect the problem and suggest the appropriate solution to that
problem. The reasoning habit enables a nurse practitioner to
learn new things. This habit develops a curiosity for a patient's
history. The nurse practitioner constructs an explanatory
hypothesis for the diagnosis of disease. I have a good memory
regarding patient history and an efficient multitasking approach
in problem-solving. Other skills are less polished, but with the
experience, I will add up those strengths as well.
Weakness during Clinical Rotation
During clinical rotation, I've faced major weakness in managing
body fluids. Also, I dislike facing pressure situations. I've
avoided dealing with patients who are not conscious of their
disease and did not follow preventive measures. These are my
weak points. These are areas to be improved. The other things I
observe as my weakness are a habit of detailing and consuming
more time on paperwork.
Methods to Overcome Barriers
The best way to get over the clinical rotation barriers is to
recognize and own your weaknesses and strengths. Always
maintain a positive and professional attitude in your work. I
consider my weakness as an opportunity to improve. The non-
serious behaviors like gossiping while attending to a patient
reduces your chance of getting a job. You should not blame
others for your mismanagement. Admit your faults and try to
improve them. Clinical rotation is a preparatory phase in your
career. Analysis of weakness and strength helps nurses get a
better job and enables them to provide quality care to their
patients. According to a study, about 10% of patients are
reported who believe that the practitioners neither listen to them
nor spend time with the patients (Babaei, & Taleghani, 2019).

11. This attitude should be eradicated, and a clear understanding
should be developed with their patients. I think maintaining a
balance between theory and experiential learning (clinical
rotation) is considered a key element in nursing education
(Karimi et al., 2017).
References
Babaei, S., & Taleghani, F. (2019). Compassionate Care
Challenges and Barriers in Clinical Nurses: A Qualitative
Study. Iranian Journal of Nursing and Midwifery
Research,https://www.ncbi.nlm.nih.gov/pmc/articles/PMC64850
23/
Karimi, S., Haghani, F., Yamani, N., & Kalyani, N., M. (2017).
Exploring the perception of nursing students about the
consequences of reflection in clinical settings.PubMed,9(9),
5191-5198,https://pubmed.ncbi.nlm.nih.gov/29038696/
ENGR 2105
Amplifiers
Dr. Kory Goldammer
Amplifiers
An amplifier increases the voltage (amplitude) of an electronic
signal, AC or DC, as shown in the figure above.
Amplifiers are found everywhere – in mobile phones, TV’s,
radios. MP3 players, small appliances, cars, etc.
Most amplifiers are linear. That is, the output is a constant (K,
called the gain) times the input (K>>1).
The Operational Amplifier (“Op Amp”)
The “op amp” typically has 5 inputs:

12. Two Inputs: ±V (normally equal magnitude + and ‒ voltages;
the power inputs). We will use the 741 Op Amp and . This is
the Maximum/Minimum voltage that can be output by the Op
Amp
Two inputs (+ and -)
One Output.
There is no ground or common terminal, although one is usually
supply supplied by the input power supply
The 741 Op Amp Chip Pin-Outs
Pin 2 is the negative input and pin 3 is the positive input
Pin 6 is the output signal
Pin 7 is where we apply 15 V, and pin 4 is where we apply -15V
Pins 1, 5, and 8 are not connected to anything
Amplifier Gain: K
The gain, K, of the Ouput is the amount of amplification. K is a
real number.
The output of most amplifiers is linear:
The Gain changes only the amplitude of the signal, so the
output signal “looks like” the input signal but with a larger
amplitude
Characteristics of the Op Amp (1)
The Op Amp shown here is configured as “Open Loop”.
“Open Loop” Op Amps have very high gain (K~100,000)

13. Such high gain is not useful. We will use a configuration
known as “Negative Feedback”
Characteristics of the Op Amp (2)
The output of the Amplifier cannot exceed
Any voltage that theoretically exceeds will have the peaks
“clipped”, and the output signal will be “distorted”
Negative Feedback
To get a useful value for the Gain, we use Negative Feedback
This technique feeds back a portion of the output signal to the
negative input
The feedback allows control of the amount of gain that the
circuit provides.
Kirchoff’s Current Law (KCL)
Kirchoff’s Current Law
The sum of the currents entering a junction must equal the sum
of of the current exiting a junction.
Negative Feedback Circuit Analysis (1)
Using KCL at Node n:
Op Amps are Designed with a very high input impedance, so we
can approximate In = 0, which means

14. Negative Feedback Circuit Analysis (2)
From Ohm’s Law:
Using these three equations and rearranging:
Negative Feedback Circuit Analysis (2)
From Ohm’s Law:
Using these three equations and rearranging:
=
Negative Feedback Circuit Analysis (3)
So, we can specify the gain simply by altering the ratio of the
feedback resistor, Rf, and Input resistor, Ri. Note that K is
negative!
=
-K: What this means
You should note in the expression for K that we developed is a

15. negative number.
This means that your amplifier inverts the signal while
amplifying it.
Thus if the input signal is some small DC voltage V, then the
output is ‒KV, K times larger than V, but of the opposite sign.
If the input is a sinusoidal AC signal v(t), then the output will
be
-Kv(t); it will be 180° out of phase with the input signal. When
the AC signal is rising above 0, the output will be falling below
0.
In a single-stage (one amplifier only) negative feedback
amplifier,
the output is always inverted compared to the input signal.
Non-Inverting Amplification
What if we don’t want an inverted signal?
For the negative-feedback amplifier circuit, a single amplifier
will always invert the sense of the output (with relation to
input).
However, op amp circuits are easy and convenient to cascade,
that is, to connect in series to increase amplification while
keeping K manageable.
Regardless of connecting amplifiers in series, each one still
inverts the signal between input and output.
Use this information for the last part of your experimental
exercises.
© N. B. Dodge 01/12

16. Op Amp Worksheet
1. Operational amplifiers have several basic characteristics ,
including high
input impedance (~ 1 Mega Ω), low output impedance (typically
< 500 Ω),
and a specific gain range. What is a typical gain of an op amp in
common devices (you
may need to do some research)?
2. The gain of an amplifier is a measure of its ability to add
power to a signal. Based
on information in the Lecture and/or Theory portion of lab,
write down a simple
gain formula in terms of input signal and output voltage:
3. The formula you develop above gives the gain of the negative
feedback amplifier,
allowing you to set the amount of gain that it will provide.
Suppose you have two
inverting amplifiers with gains of �1 = −10 and �2 = −20, and

17. you connect the
output of the first to the input of the second. What is the overall
gain of this
“cascaded” set of two amplifiers? Is the result positive or
negative? Is the output
from the second output in phase or out of phase with the
original signal?
Op Amp Data Sheet
This data sheet is for your convenience. It should not be
copy/pasted
into your report. Instead, the information you enter in the data
sheet
should be neatly typed into your report.
1. We developed an equation for the gain K of an op amp
operated in negative-
feedback mode using the values of the input resistor and
feedback resistor.
Write that formula below:
� =
��

18. ��
= __________________________
2. Calculated Gain ( = �� ��⁄ ) using the resistor values from
the lab: _____________
3. AC input signal (Vp):
__________________________
4. Measured value of amplifier output voltage (Vp):
________________________
5. Calculated Gain ( = �� ��⁄ ) using measured values in #3
and #4 above: _______
6. Resistor value of for gain of 50:
___________________
7. Amplitude of input AC signal (Vp):
__________________________
8. Amplitude of Amplifier output (Vp): _____________
9. Gain ( = �� ��⁄ ) using measured values #7 and #8:
___________________

19. 10. Calculated gain using 1K
resistor and resistor value for a gain of 50 : _____________
11. Non-inverting amplifier design: State below how you did
this. What were
the resistor values for your circuit? You can use screen shots
from
Multisim.
12. Did you use both op amps in the non-inverting amplifier? If
so, show the
circuit as a screen shot from Multisim.