The purpose of this lab is to demonstrate how to use Multisim in order to produce Bode Plots via AC Analysis. This plot will allow for a determination of the range of frequencies for which an op-amp circuit operates optimally. Students will make adjustments to external bias resistors to determine the relationship between gain and frequency in op-amp circuits.
1. Watch video Week 2 - Bode Plot
2. Construct an Active Filter (An Op-Amp configuration presented in the video) in Multisim and compute the gain of the amplifier (in db - Decibels) for the following combinations of RF and RG.
3. Perform AC Analysis to measure the gain of the amplifier (Use 5% resistor tolerances for simulation) and complete the table below:
RF RG Calculated OpAmp Gain (in db) = Vout/Vin Measured OpAmp Gain (in db) = Vout/Vin
2K? 10K?
2K? 20K?
2K? 40K?
10K? 5K?
20K? 5K?
40K? 5K?
4. Take the screen shots of bode plot for each of the above combinations of RF and RG.
5. For the Op-Amp Circuit, answer the following questions:
a. Does the measured values of the gain match the calculated values? If not, explain why they are different?
b. What is the cutoff frequency you measured from the simulation?
c. Based on the cut off frequency, what type of active filter is constructed in this lab?
d. From your measurements, explain how increase in RG affects the gain of the amplifier? How does bode plot change with increase in RG?
e. From your measurements, explain how increase in RF affects the gain of the amplifier? How does bode plot change with increase in RF?
f. What is the effect of resistor tolerance on the gain of the filter?
6. Create a new word document called "Lab2_StudentID.docx" with your GID substituted into the file name.
7. Verify all calculations from analysis and measurements from simulation. Save the results along with the table and paste the screen captures in the word document. Make sure to answer the questions.