lab 1: non-ideal operational amplifier and op-amp circuits · lab 1: non-ideal operational...

EE221-2016 Laboratory #1 2016-08-09

Rev A Copyright 2016 © University of Saskatchewan of 18

Lab 1: Non-Ideal Operational Amplifier and Op-Amp Circuits

1. Learning Outcomes In this lab, the students evaluate characteristics of the non-ideal operational amplifiers. Students use a

simulation tool (LTspice) to simulate the two most popular configurations op-amp circuits: inverting and

non-inverting amplifiers. Students also build, predict the results, and observe the gain and frequency

response of the amplifiers.

2. Health and Safety Any laboratory environment may contain conditions that are potentially hazardous to a person’s health if

not handled appropriately. The Electrical Engineering laboratories obviously have electrical potentials

that may be lethal and must be treated with respect. In addition, there are also mechanical hazards,

particularly when dealing with rotating machines, and chemical hazards because of the materials used in

various components. Our LEARNING OUTCOME is to educate all laboratory users to be able to handle

laboratory materials and situations safely and thereby ensure a safe and healthy experience for all. Watch

for posted information in and around the laboratories, and on the class web site.

3. Lab Report Students work in groups of 2 with laboratories being on alternative week (in 2C80/82). Each student must

have a lab book for the labs. The lab book is used for lab preparation, notes, record, and lab reports. The

lab books must be handed before 5:00 pm on the due date (same day of the following week) into the box

labeled for your section across from 2C94. The lab books are marked and returned before the next lab.

Marking Scheme

All labs must be performed and a lab write-up submitted in order to pass the class. If one or more labs

have not been performed, then a grade of “INC” (incomplete) will be submitted. You will be required to

demonstrate correct operation of various parts of the lab to a lab instructor during your scheduled lab

period (these parts are highlighted in the lab procedure section) to be considered as having "completed"

the lab.

A mark for each lab will be assigned based upon your submitted lab book. Lab books can be considered

to be fulfilling the same functions as logbooks in industry. Logbooks are used to record the results of all

tests performed on systems, subsystems and equipment during the various phases of a project including

R&D, design, systems integration, etc. Logbooks are official, permanent documents, and can be used in

court to prove ownership of a design!

The following points must be followed when writing up lab reports:

• The first page must contain a table of contents.

• All pages in the lab book must be numbered.

• Formal structure is not critical; logical order is important.

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• Try to use pen, avoid pencil.

• Legibility and neatness are important, as is orderly notes.

• The lab book is standalone. There should be no references to any outside documents. Remember

that you may be allowed to bring in your lab books for the final exam. They are your cheat

sheets—make sure they’re complete!

• Theory and background information must be completed prior to the lab.

• Cross out unwanted or erroneous material with a single large X. Do not remove any pages from

your lab book.

• The left-hand page can be used for rough calculations, notes, measurements, etc. This page is not

considered part of the “official” write-up, unless you ask that it be considered.

• Do not cut and paste any material from the lab manual into your lab book; only graphs, plots,

experimental waveforms, and schematics can. Use glue wherever possible; tape is acceptable,

but staples are not!

• One lab partner must have the original of any experimental waveform; his/her partner may have

a photocopy of that waveform.

• Label all diagrams and schematics; include an equipment list.

• Schematic diagrams and waveforms without explanation are not acceptable.

• Discussion of results and/or conclusions resulting from each portion of the lab should be found

with that portion. The end of the lab should have a short summary of all conclusions.

• The instructors may request you to hand-in your lab books at the end of the term for accreditation

purposes.

If in doubt about what to include (and how), remember that it should be clear, concise and complete.

4. Material and Equipment

Material

(supplied by department)

Equipment

(supplied by student)

TL082 op-amp Analog Discovery

Resistors: 2 x 1 kΩ, 1 x 10 kΩ Waveforms 2015 software

Capacitors: 1 x 470 pF Breadboard and wiring kit

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5. Prelab

Op Amp Specifications

The TL082 Op-Amp is used for this lab. The pin-out diagram for the TL082 op-amp IC is shown in

Figure 5-1.

Figure 5-1: TL082 Op-Amp

1. Go to www.digikey.ca and search for “TL082”. Select the “Linear – Amplifiers” category and apply the

“Mounting Type = Through Hole” filter. Select the “TL082IP”. Fill in the following table:

Price Break Unit Price

1

10

100

1,000

10,000

2. Using the datasheet link in step #1, make note of the following ratings/characteristics:

Rating Value

Maximum Positive Supply Voltage

Maximum Negative Supply Voltage

Input Voltage Range

Typical Loop Signal Voltage Gain

Input Resistance

Slew Rate

Gain Bandwidth

8 4

1 dot

http://www.digikey.ca/

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Inverting Amplifier

1. Analytically determine the gain of the inverting amplifier shown in Figure 6-1 (ignore the Capacitor

C1).

2. Simulate the inverting amplifier shown in Figure 6-1 using SPICE (see Appendix A on how to run

LTSpice) and include a screen shot of the output plot. A SPICE circuit file for the inverting amplifier is

shown in Figure 5-2. An on-line SPICE Reference Manual can be found at

http://www.eecg.toronto.edu/~kphang/teaching/spice/index.html

Inverting Amplifier

** Subcircuit: ideal_opamp

** Voltage controlled voltage source

.subckt ideal_opamp 1 2 3

Evcvs 1 0 2 3 1e6 ; V_1_0 = V_2_3 * 1e6

.ends ideal_opamp

** Inverting Amplifier Circuit

Vin Vin 0 DC 0 AC 100mV ; Input voltage 100 mV AC signal

R1 Vin 2 1k ; 1 kOhm input resistor

R2 2 Vo 10k ; 10 kOhm feedback resistor

C1 2 Vo 470pF ; 470 pF feedback capacitor

R3 Vo 0 1k ; 1 kOhm load resistor on output

XA1 Vo 0 2 ideal_opamp ; Op Amp subcircuit set up with negative feedback

** Analysis

.AC LIN 100 1Hz 100kHz ; AC analysis from 1 Hz to 100 kHz

.end

Figure 5-2: Inverting Amplifier SPICE Circuit File

Non-Inverting Amplifier

1. Analytically determine the gain of the non-inverting amplifier shown in Figure 6-7 (ignore the

Capacitor C1).

2. Simulate the non-inverting amplifier shown in Figure 6-7 (include the Capacitor C1) using SPICE and

include a screen shot of the output plot. You will need to modify the SPICE circuit file from the

inverting amplifier.

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Breadboards

1. Watch the video at "https://www.youtube.com/watch?v=oiqNaSPTI7w".

2. Answer the following questions:

2.1. Why is it called a breadboard?

2.2. What feature makes it easy to connect to the power supply?

Resistors

1. Watch the video at "https://www.youtube.com/watch?v=SjlnW5g9np4".

2. Answer the following questions (a Resistor Colour Code Chart can be found in Appendix B):

2.1. What would be the colour code of a 2.2 kΩ resistor with 5% tolerance?

2.2. A resistor has colour code Brown-Black-Orange-Gold. What is its resistance value?

2.3. A resistor has colour code Brown-Black-Black-Brown-Brown. What is its resistance value?

3. You can also download one of a number of apps to your smartphone for identifying resistors (e.g.

Resistor Color Code for Android).

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6. Lab Procedures

Debugging (or What To Try When Things Aren't Working)

There are a number of things/procedures you should use to debugging circuits when things are not

working correctly. These include (but are not limited to):

Check that all component pins are correctly inserted in the breadboard (sometimes they get bent

underneath a component).

Make sure that components are not "misaligned" in the breadboard (e.g. off by one row).

Double check component values (you can measure resistors, capacitors, and inductors).

Try a different section in the breadboard (in case there is a bad internal connection).

Measure the source voltages to verify power input.

Measure key points in the circuit for proper voltage/waveform (i.e. divide-and-conquer).

Inverting Amplifier

One of the most common applications of the op-amp is the simple inverting amplifier. The output is

inverted relative to the input and the amplification gain is determined by the ratio of the feedback resistor

(R2) to the input resistor (R1).

1. Construct the circuit shown in Figure 6-1 on your breadboard. A Resistor Colour Chart can be found

in Appendix B and an Analog Discovery Pin Out in Appendix C:

1.1. The +5 V supply is provide by V+ of the Analog Discovery (red wire) and the -5 V supply is

provided by V- of the ADM (white wire).

1.2. Vin is supplied by the Arbitrary Waveform Generator W1 (yellow wire), make sure to include at

least one ground (black wire).

1.3. An example of a circuit layout with above connections is shown in Figure 6-2.

1 kΩ R3

C1

470 pF

Vin

Vo+

_

+5 V

-5 V

R2

10 kΩ

R1

1 kΩ TL082

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Figure 6-1: Inverting Amplifier Circuit Schematic

Figure 6-2: Inverting Amplifier Example Layout

2. Use "Supplies" on Waveforms 2015 to turn on the V+ and V- supplies.

3. Set "Vin" to be a 100 mV 1 kHz sine wave using the "WaveGen" tool as shown in Figure 6-3 and turn

on by pressing "Run".

Figure 6-3: Arbitrary Waveform Generator 1 Setting

4. Connect "Channel 1" to measure the input voltage "Vin" (relative to ground). Channel 1 is the voltage

difference between 1+ (orange wire, also called "Scope Channel 1 Positive") and 1- (orange/white

wire, also called "Scope Channel 1 Negative").

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5. Connect "Channel 2" to measure the output voltage "Vo" (relative to ground). Channel 2 is the voltage

difference between 2+ (blue wire, also called "Scope Channel 2 Positive") and 2- (blue/white wire,

also called "Scope Channel 2 Negative").

6. Bring up the Scope window by selecting "Scope" from the WaveForms main screen. Press "Run" and

the Scope window should look similar to Figure 6-4 if everything is working correctly.

Figure 6-4: Initial Scope Window

7. To be able to better see and measure the waveforms:

7.1. Set "Time Base" = 200 us/div, set "C1 Range" = 50 mV/div and set "C2 Range" = 500 mV/div.

Turn off “Noise” for both channels (refer to Lab 0 if you need instructions).

7.2. Click on the "View | Measure" option and "Add":

7.2.1. "Channel 1 | Horizontal | Frequency"

7.2.2. "Channel 1 | Vertical | Amplitude"

7.2.3. "Channel 2 | Vertical | Amplitude"

7.3. Click on "Single" to freeze the capture and read off the Measurements.

7.4. The Scope window should look similar to Figure 6-5:

7.4.1. Include a screen capture in your report.

7.4.2. Note that the output waveform should have an amplitude 10 times larger than the input

waveform and that they are 180o out of phase with each other (e.g. when the input

reaches a peak, the output reaches a valley). The Gain is -10.

7.5. REQUIRED: Demonstrate to a lab instructor and make sure your demonstration is recorded

by the lab instructor.

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Figure 6-5: Scope Window With Measurements

8. Measure and fill in the values for the table below (be sure to include units). You will need to adjust

"Time Base" so that the sine waves are discernable as you change frequency.

Frequency Vin Amplitude Vo Amplitude Gain = |Vo/Vin| Modeled Vo from Prelab

1 kHz

5 kHz

10 kHz

Every 10 kHz until 100 kHz

9. Comment on what happens to the relative "phase" (delay) between the input and output voltages

when the frequency is changed from 1 kHz to 100 kHz. Get a screen capture of the Scope at 100 kHz.

10. Determine the frequency at which the gain equals 0.707 of the maximum gain:

10.1. This is most easily accomplished by determining the target Vo, and using the slider on the

Frequency parameter in Wavegen (change “Simple” to “Basic”, see Figure 6-6). Move the slider

until the "C2 Amplitude" closely matches as possible to the target Vo. Note that setting

appropriate "Max" and "Min" value for the slider makes it easier. You may need to adjust "Time

Base" so that you only see a few cycles of the sine waves (to get reasonable measurements) as

you change frequency.

10.2. Include a screen capture of the Oscilloscope window showing the found 0.707 gain point.

10.3. Is there a specific name for this frequency?

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Figure 6-6: Basic Waveform Generator Mode

11. Remove Capacitor C1. Measure and fill in the values for the table below (be sure to include units):

Frequency Vin Amplitude Vo Amplitude Gain = |Vo/Vin|

1 kHz

5 kHz

10 kHz

20 kHz

50 kHz

100 kHz

12. Plot the output voltage Vo versus Frequency for the measured Vo from step 6.2.8 and step 6.2.11 and

the simulated Vo from Prelab 5.2.

EE221-2016 Laboratory #1 2016-08-09


Non-Inverting Amplifier

1. Construct the circuit shown in Figure 6-7 on your breadboard.

1 kΩ R3

C1

470 pF

Vin

Vo+

_

+5 V

-5 V

R2

10 kΩ

R1

1 kΩ TL082

Figure 6-7: Non-Inverting Amplifier Circuit Schematic

2. Set "Vin" to be a 100 mV 1 kHz sine wave.

3. Connect "Channel 1" to measure the input voltage "Vin" and connect "Channel 2" to measure the

output voltage "Vo".

4. Similar to section 6.2, bring up the Scope window and adjust its parameters (including the

Measurement functions) to provide a good picture of the input and output voltages. Include a screen

capture in your report.

4.1. REQUIRED: Demonstrate to a lab instructor and make sure your demonstration is recorded

by the lab instructor.

5. Measure and fill in the values for the table below (be sure to include units):

Frequency Vin Amplitude Vo Amplitude Gain = |Vo/Vin| Modeled Vo from Prelab

1 kHz

5 kHz

10 kHz

Every 10 kHz until 100 kHz

6. Comment on what happens to the relative "phase" (delay) between the input and output voltages

when the frequency is changed from 1 kHz to 100 kHz.

7. Determine the frequency at which the gain equals 0.707 of the maximum gain. Include a screen

capture of the Oscilloscope window showing the found 0.707 gain point.

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8. Remove Capacitor C1. Measure and fill in the values for the table below (be sure to include units):

Frequency Vin Amplitude Vo Amplitude Gain = |Vo/Vin|

1 kHz

5 kHz

10 kHz

20 kHz

50 kHz

100 kHz

9. Plot the output voltage Vo versus Frequency for the measured Vo from step 6.3.5 and step 6.3.8 and

the simulated Vo from Prelab 5.3.

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Appendix A – SPICE "SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose, open source analog

electronic circuit simulator. It is a powerful program that is used in integrated circuit and board-level

design to check the integrity of circuit designs and to predict circuit behavior" (from Wikipedia).

There are a number of freeware SPICE simulation programs available. "LTspice IV" is available on the

Engineering computers in the "Electrical Engineering" folder under the Start menu. It can also be

downloaded to your home computer from http://www.linear.com/designtools/software/#LTspice.

To run a simulation:

1. Create a text file with the SPICE circuit description with a ".cir" extension (a good Windows text editor

is Notepad++ can be found at https://notepad-plus-plus.org).

2. Run "LTspice IV" and "File | Open" the file from step 1 (make sure you select "Files of type: Netlists

(*.cir, *.net, *.sp)"). Your screen should look similar to Figure A-1.

Figure A-1: LTspice IV Circuit Description

3. Select the "Simulate | Run" menu item to run the simulation. A blank plot window should be opened

as shown in Figure A-2.

4. Select the "Plot Settings | Add trace" menu item. Select the "V(vin)" and "V(vo)" traces to plot as

shown in Figure A-3.

5. Maximize the plot window. The screen should look similar to Figure A-4. Note that the vertical scale

is in "dB". Change the range using the "Plot Settings | Manual Limits" menu item to match what is

shown in Figure A-5. Also “Plot Settings | Grid”. The final plot window should now look similar to

Figure A-6.

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Figure A-2: Initial Plot Window

Figure A-3: Add Traces Dialog

Figure A-4: Maximized Plot Window

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Figure A-5: Plot Limits Dialog

Figure A-6: Final Plot

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Appendix B - Resistor Colour Codes

http://itll.colorado.edu/electronics_center/resistor_chart/

EE221-2016 Laboratory #1 2016-08-09


Appendix C - ADM Pin Out

lab 1: non-ideal operational amplifier and op-amp circuits · lab 1: non-ideal operational...

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