Objective Information The purposes of this laboratory project are for the student to observe an inverting operational amplifier circuit, to demonstrate how the resistors in an operational amplifier circuit affect gain, and to demonstrate the limitation of slew rate and the output voltage swing of an operational amplifier. Operational Amplifiers Operational amplifiers (op amps) are nearly ideal amplifiers that are quite simple to use. An op amp behaves as a voltage controlled voltage source, with a gain factor that is dependent upon the arrangement of components surrounding it. The op amp for this laboratory project is in an 8 pin dual inline package. The arrangement of the pins and the function of the pins is shown below. Fig. 1 shows the pin function of the OP27 operational amplifier along with the pin 1 indicator. As can be seen from the figure above, the op amp circuit above consists of two input pins, an output pin, supply voltage pins and three pins that we need not consider for purpose of this laboratory project. The two supply pins, once connected provide power for the circuit, are generally not considered in the analysis of the circuit. The general schematic of the circuit for this laboratory project is given in the figure below. Fig. 2 shows the inverting configuration of an op amp. 1 of 6
Procedure Measure and record the values of all resistors that will be used in this project. In EGH337: DO NOT TURN ANY OF THE VOLTAGE SUPPLIES ON UNTIL INSTRUCTED TO IN THE PROCEDURE. Begin construction of the circuit by inserting the op amp into the breadboard so that it spans one of the center grooves of the breadboard. The first two connections that should be made are connecting Pin 7 (Vpos) of the op amp to the +20V terminal of the power supply and connecting Pin 4 (Vneg) of the op amp to the 20V terminal of the power supply. Construct the circuit shown in Figure 2 using the following component values: Ri=1kΩ, Rf=2.2kΩ, and Rload=1kΩ. Use a BNC to micro clip connector to connect the function generator into the circuit as vsig. The ground of the circuit should be the COM terminal of the DC power supply. The black micro clip from the function generator should be connected to the circuit common. The oscilloscope will be used to view the input and output signals. Connect channel 1 of the oscilloscope to the same points of the circuit as the function generator. Channel 2 of the oscilloscope will be used to observe Vout. Be sure that all of the black micro clip leads connect to the common of the circuit. After the circuit is constructed, and all connections are checked: 1. Turn the +6V and 20V knobs on the DC power supply fully counter clockwise. 2. Turn on the DC power supply and select the 20V setting, and slowly increase the voltage at the +20V output to 5V. Monitor the current as the voltage is increased, and if the current exceeds 0.02 amps immediately power down and recheck the wiring of the circuit. 3. Configure the function generator as follows: a. Set the amplitude of the function generator output to 250mVpp (remember from the previous project that the actual output will be twice this value). i. Make sure Ampl is highlighted on the screen and enter 250. ii. Press the button under mvpp on the display screen b. Set the frequency of the function generator output to 10kHz i. Press the button under Freq on the screen and enter 10 ii. Press the button under khz. iii. Do not forget to press the output button of the function generator. c. Adjust the settings on the oscilloscope so that 2 3 wave cycles appear on the screen and so that the amplitude of the waves from channel one and two are both clearly displayed on the oscilloscope screen without overlapping. i. If Rmt appears on the oscilloscope screen, it is necessary to press Force Trigger (Local) to establish local control over the oscilloscope. d. To display the waveforms, adjust the horizontal control at the top (this controls the seconds per division) and vertical controls, which are the large yellow and green knobs (these control the volts per division). e. Press the Meas button on the oscilloscope. f. Adjust the measurement settings to select the peak to peak voltage and frequency of channel 1. i. To change the channel of the measurement, press the button next to Source on the screen until CH1 is selected. ii. Press the button next to Voltage. 1. Use the highlighted knob to select Vpp and press the knob. iii. Press the button next to Time. 1. Use the highlighted know to select Freq and press the knob. g. Adjust the measurement settings so that the bottom two measurements give the peak to peak voltage of channel 2 i. Press the button next to Source to select CH2. 2 of 6
ii. Select Vpp under the Voltage menu. h. Open a Word document and open Intuilink from the computer desktop. i. If the program is not in the Windows menu it is found in: C:\Program Files (x86)\agilent\intuilink\data Capture 1. The program is named agtdtcpt2.exe Downloading images from the Keysight 1xxx series oscilloscopes. ii. In any operation of the Keysight oscilloscope if Rmt appears on the screen press Force Trigger (Local) to enable the oscilloscope inputs. iii. With the oscilloscope on start Intuilink Data Capture from Windows. 1. Under Instrument select Agilent 1000 Series 2. Under the Set I/O tab, click Find Instrument 3. Under Select Address(es), select the address beginning with USB 4. Click Identify Instrument(s) 5. Select the oscilloscope and click OK to close the Find Instrument dialog box 6. Click OK on the Agilent 1000 Series Add In dialog box 7. At this point two windows should appear within the Agilent Intuilink Data Capture window. a. One is a screen shot that can be copied as an image. i. This can be copied and pasted into a Word document or saved as a png or bmp. b. One is an text data file. i. This can be imported and manipulated in a program like Excel. 8. To download another image click on the Get Data icon. i. Download the oscilloscope image to the Word document i. The resolution of the image is dependent upon the size of the window when the screen is captured, so maximize the screen window before capturing data. Press Run/Stop before downloading the screen. 1. If the image does not paste with the correct orientation: a. Right click on the image and select Size and Position b. Under absolute height enter 3 inches c. Under rotation enter 90 degrees d. The image should now be upright and of an appropriate size for a document. 2. If the image is oriented correctly, resize the image using the above procedure. ii. Save your Word document to your user drive. iii. Press Run/Stop to perform the next measurement. 4. Adjust the output from the function generator to 500mV peak to peak. a. Repeat the procedure in step 3c i to download the measurement to your document. 5. Return the output of the function generator to 250mVpp. 6. Turn off the DC power supply and replace the 2.2kΩ feedback resistor with a 4.7kΩ resistor. 7. Turn the DC power supply on with ±5V supplies. 8. Download the image from the oscilloscope (make sure the measurements are set 9. Change the output setting of the function generator to 500mVpp. a. The output of the operational amplifier circuit should have the top and bottom of the waveform cut off. If it does not, ask the instructor or laboratory assistant for help. 10. Download the image from the oscilloscope (make sure the measurements are set 3 of 6
11. Adjust the DC power supply until the output of the operational amplifier circuit is not clipped off anymore, but may still be distorted (i.e. not quite a sinusoidal wave, but close). This step is to allow the student to observe the effect of the DC power supply. 12. Return the DC power supply to ±5V 13. Return the output of the function generator to 250mVpp. 14. Adjust the frequency of the input to 250kHz. (The output waveform should look like a triangle waveform.) 15. Download the image from the oscilloscope (make sure the measurements are set 16. Adjust the output of the function generator to 100mVpp. (The output waveform should be sinusoidal again.) 17. Download the image from the oscilloscope (make sure the measurements are set 18. Turn off the function generator, then the DC power supply. 19. Disassemble your circuit and put all of the leads and parts away. Using the Analog Discovery: DO NOT TURN ANY OF THE VOLTAGE SUPPLIES ON UNTIL INSTRUCTED TO IN THE PROCEDURE. Begin construction of the circuit by inserting the op amp into the breadboard so that it spans one of the center grooves of the breadboard. The first two connections that should be made are connecting Pin 7 (Vpos) of the op amp to the +5V supply and connecting Pin 4 (Vneg) of the op amp to the 5V supply. Construct the circuit shown in Figure 2 using the following component values: Ri=1kΩ, Rf=2.2kΩ, and Rload=1kΩ. Connect the wave generator into the circuit as vsig. The oscilloscope will be used to view the input and output signals. Connect channel 1+ of the oscilloscope to the same point of the circuit as the wave generator. Channel 2+ of the oscilloscope will be used to observe Vout. Both of the negative oscilloscope leads must be connected to ground. After the circuit is constructed, and all connections are checked: 1. Turn on the supplies. If the supplies do not remain on, check your wiring. 2. Configure the wave generator as follows: a. Set the amplitude of the function generator output to 250mVpp (to do this you will have to change to basic mode). i. Click one the dropdown menu (default is Simple). ii. Enter 250 for the amplitude. b. Set the frequency of the function generator output to 10kHz i. Set the frequency range to go from 1kHz to 1MHz ii. Enter 10 khz for the frequency. iii. Click on Run. c. Add the Scope to the workspace. i. Adjust the settings on the oscilloscope so that 2 3 wave cycles appear on the screen and so that the amplitude of the waves from channel one and two are both clearly displayed on the oscilloscope screen. d. To accomplish this, adjust the Time Base and the Range of the channels if necessary. e. Under the View menu, click on Measurements i. Add Defined Measurement Channel1 Vertical Peak2Peak ii. Add Defined Measurement Channel2 Vertical Peak2Peak iii. Add Defined Measurement Channel1 Horizontal Frequency f. Open a Word document. g. Download the oscilloscope image to the Word document i. The simplest way to do this may be grabbing the scope window and measurements using the snipping tool. 4 of 6
1. If the image does not paste with the correct orientation: a. Right click on the image and select Size and Position b. Under absolute height enter 3 inches c. Under rotation enter 90 degrees d. The image should now be upright and of an appropriate size for a document. 2. If the image is oriented correctly, resize the image using the above procedure. ii. Save your Word document to your user drive. 3. Adjust the output from the function generator to 500mV peak to peak. a. Repeat the procedure in step 3g to download the measurement to your document. 4. Return the output of the function generator to 250mVpp. 5. Turn off the DC power supply and replace the 2.2kΩ feedback resistor with a 4.7kΩ resistor. 6. Turn the DC power supply on with ±5V supplies. 7. Download the image from the oscilloscope (make sure the measurements are set 8. Change the output setting of the function generator to 500mVpp. a. The output of the operational amplifier circuit should have the top and bottom of the waveform cut off. If it does not, ask the instructor or laboratory assistant for help. 9. Download the image from the oscilloscope (make sure the measurements are set 10. Return the input to a voltage where the output is not clipped. 11. Reduce the DC power supplies symmetrically until the output of the operational amplifier circuit is clipped or distorted (i.e. not quite a sinusoidal wave, but close). This step is to allow the student to observe the effect of the DC power supply. 12. Return the DC power supply to ±5V 13. Return the output of the function generator to 250mVpp. 14. Adjust the frequency of the input to 250kHz. (The output waveform should look like a triangle waveform.) 15. Download the image from the oscilloscope (make sure the measurements are set 16. Adjust the output of the function generator to 100mVpp. (The output waveform should be sinusoidal again.) 17. Download the image from the oscilloscope (make sure the measurements are set 18. Turn off the function generator, then the DC power supply. 19. Disassemble your circuit and put all of the leads and parts away. Assignment Create a document following the informal laboratory report format that includes the following content and sections. 1. Report Header 2. Summary Use your own words. 3. Data Include all measurements (this includes all of the images) and all observations from this project. 4. Discussion 5 of 6
Answer the following: Are there any general observations you are able to make with respect to the operation of inverting operational amplifier circuits? How do the expected (theoretical) output voltages compare to the measured output voltages? How does the DC power supply affect the output of the circuit and the integrity of the signal? How does the frequency of the input and the gain of the amplifier affect the output of the circuit and the integrity of the signal? All tables, graphs, and figures must be descriptively captioned. Check off In order to receive credit for performing this laboratory project it is necessary to have the instructor or student assistant review your data. The data must then be submitted for the laboratory project data assignment in Canvas for this project (only files in pdf are accepted). 6 of 6