Reference no: EM132397181
Multisim Electronics Circuit Designing And Simulation Task -
Objective - After completing this laboratory, a student should be able to:
Calculate the Fourier Series of a periodic waveform.
Perform a frequency spectrum analysis of a periodic and non-periodic waveform.
Use a Bode plot to compare the frequency response of different components.
Calculate the Total Harmonic Distortion (THD) of a signal.
Equipment - Students will need the use a computer for the simulations and analysis.
Parts I & II -
National Instruments circuit simulation program MULTISIM.
MATLAB or Matlab (or similar) high-level interactive computing environment.
Microsoft EXCEL spreadsheet program and WORD word-processing software (or equivalent).
Part I - The Fourier Series / Frequency Spectrum Analyzer
1. Locate Multisim by going to the search bar and typing in "Multisim" in the search window. Start the program (it may take several seconds to load) and begin with a blank work area. Be sure and save your circuit file routinely as you proceed through with the lab.
2. Bring the Function Generator into the work area along with the two-channel generic Oscilloscope. Make sure to place a ground in your circuit. If you do not the simulation will not run and/or you will get erroneous results.
3. Wire the output of the "+" terminal of the generator to the "+" input of Channel-A on the oscilloscope. Wire the "Common" terminal of the generator to the "-" input of Channel-A and ground.
4. Configure the Function Generator to produce a sinewave, v(t), at a frequency of 10 kHz and 10V for VPK.
If you do not see the red "node" (Multisim refers to them as "nets") numbers on your circuit make sure nothing is selected on your circuit and then click on the "Edit" tab up in the ribbon and select the "Properties" option located at the bottom of the list. A "Sheet Properties" dialogue box should pop up and on the "Sheet Visibility" option make sure the radio button is selected so that all "Net Names" are displayed. Click OK and you should not see them on the screen. Note that the ground node is always listed as node "0".
5. Run the simulation for a few seconds and then stop it. Adjust the horizontal and vertical scales of the Oscilloscope so that 2-4 periods of the sine-wave are visible.
6. Measure the time for one period of the waveform using the cursors on the oscilloscope. This is "T" for the periodic waveform and recall that T is equal to the inverse of the frequency or T = 1 / f. Verify that the inverse of the period is equal to the frequency "f".
7. To obtain a higher quality trace you can click on the "View" tab up in the ribbon and then go down and click on the "Grapher" or Grapher View). You will need to adjust the scales and add labels (right-click on what you want to change and select the option).
8. Close the Oscilloscope front panel and bring in the Frequency Spectrum Analyzer by going to Simulate -> Instruments - > Spectrum Analyzer or by selecting it from the instrument panel. Connect the single input to the output of the Function Generator (same line as Channel-A of the Oscilloscope).
9. Select the Spectrum Analyzer and open the properties box. Set the Span to 50 kHz, minimum of 0Hz (DC), center of 25 kHz, and maximum of 50 kHz and then click ENTER. Next set the resolution to 1 kHz. Run the simulation.
10. Move the cursor over and measure the amplitude and frequency of the "peak" that is displayed. (See diagram). Record the Frequency (x-axis) and Voltage amplitude (y-axis) values. How do these compare with the settings on the function generator? (Note that a higher-quality trace can be obtained in the "Grapher View").
11. Stop the simulation and change the Function Generator so that it produces a square wave. Adjust the Span values so that the frequency range is from 0 Hz to 120 kHz with a center frequency of 60 kHz. Run the simulation and see what frequencies are displayed now (ignore the very small ones). Record the fundamental frequency (frequency and amplitude) as well as the first 4 non-zero harmonics (ie. (V0, f0), (V3, f3), (V5, f5), (V7, f7), (V9, f9)).
12. Repeat the step above with a triangle wave...same amplitude and frequency.
13. Calculate the Fourier Series coefficients for both the square and triangle waves (see Appendix A for the formulas) and compare with your measured values. Comment on the results.
We will now use the results obtain for the square wave and see if we can reproduce those using single sinusoidal sources.
14. Build the following circuit in Multisim. Note that you can put together one source, SPST switch, and ground together and then replicate it as many times as you need to using the Copy and Paste function. You will need to set the frequencies and amplitudes of each of the sources to match those you obtained with the Frequency Spectrum Analyzer.
15. Change the "Key" setting of the switches so they toggle using different keys on the keyboard.
16. Set the frequencies and amplitudes of the Function Generators so that they represent the fundamental frequency and the first 4 harmonics that you obtained for the square wave.
17. Bring in the Oscilloscope and connect it up to the output, VOUT.
18. Close the first switch of the Function Generator set for the fundamental frequency. Run the simulation and adjust the settings on the Oscilloscope to produce 2-4 periods of the waveform. Is the Oscilloscope showing the sine wave? Obtain a screen capture of the waveform (you can use the "Snipping" tool located in the Accessories folder).
19. Add a second function generator, representing the next non-zero harmonic. What does the waveform look like now?
20. Continue closing the switches and note the shape of the waveform. How close to a square wave does it appear?
21. Repeat the above for the triangle wave and see how close the reconstructed waveform comes to an ideal triangle wave.
Part II - Bode Plots & Distortion
(Refer to Appendix B for information about Bode plots and Distortion)
1. Construct the inverting op-amp (VOUT/VIN = AV = 5) circuit shown below using an LM741H IC (you will find this in the component "library" of Multisim). Note that you need to "bias" the op-amp with two DC power supplies wired to produce -15V DC (pin 4) and +15V (pin 7). Use a Function Generator as the input source set for a sine wave at 1 kHz and 1 VPK.
2. Calculate the gain in dB's of the amplifier in the passband region using the following equation:
dB = 20log(VOUT/VIN) = 20log(AV) = _______ dB's
3. Also calculate the value (in dB) of the half power points for the amplifier given the gain in the passband above (i.e. What would the value of the gain be in dB?)
4. Bring in an Oscilloscope and Bode plotter from the instrument menu and connect to your circuit as shown. Note you will need to hook up inputs AND outputs for the plotter so it can accurately determine the gain. Go to Simulate -> Instruments -> Bode Plotter or select it from the instrument panel. Connect the INPUT of the Bode plotter to the output of the function generator and the OUTPUT to the output of the circuit.
5. Open the properties box of the Bode plotter. Set the initial and final values for frequency and output. Specify "magnitude" for the output display. Note you made need to adjust the scale on the Bode plotter. There is a cursor that can be used to obtain readings from the display.
6. Turn on the circuit and you should see the frequency response on the Bode plotter. Move the cursor until you obtain one of the half-power points based on your value of what the dB should be at that point. (Note: you may only have one half-power point rather than two...why?) Obtain copies of the Bode plotter and include with your laboratory report. Record the frequency value of the half-power point(s).
7. Make a "clone" of your circuit and put it on a different work sheet in Multisim.
8. Change the model of op-amp used to a TL082CP. Select the op-amp and click on "Replace component(s)". Select the new op-amp from the list or type it in as a search.
9. Repeat the measurement analysis for this op-amp. Is the half-power frequency the same? Would there be any advantage to using this type of op-amp versus a 741?
10. Change the op-amp back to the LM741H in your circuit and remove the Bode plotter. Put the oscilloscope in and connect Channel-A to the output of the Function Generator and Channel-B to the output of the op-amp.
11. Set the frequency of the function generator to 1 kHz and the amplitude to 4 volts (0 to peak value). Turn on the simulation and record the input and output waveforms. Do you see "clipping" on the output?
12. Perform a Fourier analysis of the output of the circuit. Click on the "Simulate" icon in the toolbar and then select "Analyses" and then "Fourier Analysis...". Specify the fundamental frequency (1kHz) and go out 20 harmonics. Click on the "Output" tab and then select the output "line" of the op-amp. Click the simulate tab down towards the bottom of the menu.
13. Calculate the value of the THD using the formula given in Appendix B. Compare with the value listed in Multisim.
Attachment:- Multisim Electronics Circuit Designing And Simulation.rar