Report6

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3112L

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Electrical Engineering

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Feb 20, 2024

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FAMU-FSU College of Engineering Department of Electrical & Computer Engineering EEL3112L – Advanced Circuits with Computers Laboratory LAB REPORT 6 FALL 2023 Experiment: 6 – Operational Amplifiers Date: October 17, 2023 Author: Oriana Matney List of partners: Luis Victores, William Lucky Instructor: Dr. Jinyeong Moon TA: Ahmad Abdelhadi

Contents Abstract ............................................................................................................................................ 2 1. Introduction .................................................................................................................................. 2 2. Experimental procedure ............................................................................................................... 3 3. Results .......................................................................................................................................... 5 4. Discussion .................................................................................................................................... 9 5. Conclusion and Recommendations ............................................................................................ 10 Abstract : The purpose of this experiment was to expose students to transient behaviors of RC circuits as well as their frequency responses. This process involved the creating of an RC circuit with which the students conducted multiple experiments with. Firstly, the students measured the component values and calculated time constants of the circuit using knowledge from previous labs. After this was established, students ran experiments and measured values as well as used graphical data from oscilloscope readings to understand how frequency values affect RC circuits. Students used the oscilloscope outputs and cursors to measure max and min voltage values, RMC voltage values, and calculate the gain of the circuit. While these measurements are useful, the key finding of these types of experiments was to understand how different frequencies allow or prevent capacitors from reaching a steady state. Another experiment in this lab exposed students to the frequency response of the same circuit but through the use of a bode analyzer. The students generated graphical data of the RC circuit used in previous experiments to measure the 3dB cutoff frequency, then, using the same components, the students swapped the locations and completed the same procedure. The key finding from these frequency response experiments was to teach the students how placement of RC circuits affects the response and can change the type of filter created from the placements. Lastly, while there was no necessary measured data, the students created a circuit consisting of a transistor, two resistors, and an LED to create an electronic device. This device resulted in a blinking light and while there may not be any large takeaways from this experiment, it was fundamental to the students learning of RC circuits and what they can be used for. 1. Introduction A Problem Statement: Students have little to no experience with simulations and measurements of op-amps and their behaviors. The Purpose and Justification of the Experiment:

The purpose of this experiment was to expose students to inverting and non-inverting op-amps, the gain-bandwidth product of op-amps, as well as voltage followers and frequency responses of op-amps. This benefits the students’ future educational careers. The Scope of the Experiment: This experiment covered a few ideas surrounding RC circuits as well as some extra information on transistors and LEDs. The majority of this lab covered transient behavior of an RC circuit and using a bode analyzer to measure the frequency response of an RC circuit. The last experiment of this lab introduced the students to transistors and what they are capable of through the use of an LED. 2. Experimental procedure The hardware for this experiment consisted of three resistors, an LED, capacitor, transistor, NI ELVIS III prototype board, and a computer capable of running the associated NI ELVIS III software. Some preliminary experiments for this lab required the students to denote, measure, and calculate the error percentage of the three resistors and the capacitor. The circuit seen in Figure 1 was provided in the lab manual for experiment 13.1. The students were required to build this circuit on the pb using the built-in function generator as well as the programmable AI ports. Figure 1: Provided Circuit for Experiment 13.1-13.3. The students were also provided with the following information for the function generator: amplitude = 1Vpp, DC Offset = 1V, frequency 1/(4τ) Hz, and a 50% duty cycle. It was implied that the students found τ using previous lab knowledge. Using the oscilloscope, the students adjusted the viewing terminal to output a clear graph and then clicked the red stop button to take measurements for Table 1. Table 1: Measurements taken for experiment 13.1. Waveform Max. Value Min. Value RMS Value Gain G v (dB) v s v o

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The students then logged the oscilloscope data as a text file and recreated the graph in MATLAB or Excel using knowledge from previous labs or prelab 13. The students were asked to analyze and interpret the measurement results to finish this experiment. Experiments 13.2 and 13.3 followed the same exact procedure for 13.1, except with frequency values of 1/(8τ) Hz and 1/(10τ) Hz respectively. For experiment 13.4, the students made a few adjustments to the already established circuit in order to use the bode analyzer as in the circuit diagram in Figure 2. Figure 2: Provided Circuit for Experiment 13.4. The students were also provided with Figure 3 to adjust the parameters of the bode analyzer. Figure 3: Provided Bode Analyzer Parameters for Experiment 13.4. After running the simulation, the students were required to use plot cursors to measure the 3dB cutoff frequency. Again, the final steps of this experiment were to log the data, create a plot of the data in either MATLAB or Excel, and then analyze and interpret the results. In experiment 13.5, the students were asked to switch the locations of R1 and C and repeat the same procedure as in 13.4. For the last experiment of this lab, the students created the circuit as seen in Figure 4.

While no data was collected, the results from this circuit were to be checked by the Lab TA and can be seen in the results section of this report. Figure 4: Provided Circuit for Experiment 13.6. 3. Results Preliminary Measurements of Part A Circuit Component Measured Value Resistor R1 (kΩ) 66.67 Resistor R2 (kΩ) 198.80 Resistor R3 (Ω) 100.41 Resistor R4 (Ω) 201.27 Resistor Rs (kΩ) 1.48 Resistor RF (kΩ) 99.13 Resistor RL (kΩ) 4.66 Capacitor C+ (nF) 33.3 Capacitor C- (uF) 0.9577 Measured Values of the voltage follower output of Part B

Voltage Follower Output Voltage Vo (V) Built without an op-amp 14.785m Built with an LM741 op-amp 2.1 It should be noted that after Part B, the students equipment was not working and instead finished the lab using Multi-Sim. 4. Discussion The results of this lab were very close to the expected theoretical results. This lab had the purpose of teaching students the transient behaviors of RC circuits as well as their frequency responses. This was accomplished through the use of an RC circuit with a function generator set to a square wave of varying frequencies. The change of frequency was to show how the student can set timing of a circuit to prevent or allow a capacitor to reach a steady state. As for frequency responses, students used the same RC circuit connected to a bode analyzer instead of a function generator to measure the corresponding 3dB cutoff frequency. This allowed the student to understand what type of filter an RC circuit can be depending on the placement of components. There was not a lot of room for error in this lab other than the last experiment. It was important that students understood the pin diagram of a transistor as to not destroy the device by making the wrong connections. As this was not the case in this experiment, the students found that their device was not working from previous error. This was found when power was given to the circuit after the TA double checked connections and could only be fixed through the provision of another transistor. This lab served its purpose of teaching students about RC circuit behavior and response. 5. Conclusion and Recommendations This lab did well to complete its goals of familiarizing students with transient behavior and frequency responses of RC circuits. This was completed through experiments with varying frequencies as well as switching the placement of the resistor and capacitor respectively. The student also saw how this circuit can be used in electronic devices by creating a blinking LED with a transistor. This experiment was extremely successful in its purpose and should not be redesigned.

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