W4 -Lab 4 Comparator-OL 2023-06

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ECPI University, Virginia Beach *

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Electrical Engineering

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Jan 9, 2024

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Experiment 4: Comparators Objectives: After completing this experiment, you should be able to, 1. Observe the behavior of Op-Amp as a comparator. 2. Build and test op-amp as a zero-level detector/sine-to-square wave convertor. Submission Requirements: Submit the Multisim.ms14 file along with your Experiment 4 lab document. Components needed: Instruments used: 1. Potentiometers: 1kΩ, 10kΩ 1. Digital Multimeter (DMM) 2. Op-Amp: (1) LM741CN 2. Oscilloscope Procedure: 1. The LM741C is 8-pin op-amp. The pinout is shown in Figure 1. Observe there is a notch and a dot on the IC. The left side pin to the notch/dot is pin 1. Figure 1: LM741 Pinout and Breadboard placing
2. Construct the following circuit shown in Figure 2 in MultiSim. Figure 2: Op-Amp Comparator Place Your Schematic Here with voltage measurement probes Display results for row 1 of Table 1
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3. Measure the voltage at pin 3 using a voltage probe and adjust the 10kΩ potentiometer according to the voltage listed in Table 1. 4. Measure the voltage at pin 2 using a voltage probe and adjust the 1kΩ potentiometer according to the voltage listed in the first row of Table 1. 5. Measure the output voltage at pin 6 using a voltage probe and record the result in Table 1. Pin 3 V+ Pin 2 V- Pin 6 V OUT 1V -1V 14 5V -6V 14 -2V 7V -14 -5V 10V -14 Table 1: Calculated and measured values
6. Repeat step 3 through 5 for various voltage values at pin 3 and pin 2 as shown in rows 2,3, and 4 in Table 1. 7. Modify the above circuit as shown in Figure 3. Note that pin 3 is now connected to the function generator Figure 3: Op-Amp Comparator sine-to-square wave convertor Place Your Schematic Here
8. Set function generator to 10V PP , 1 kHz sinewave. 9. Connect CH_A of the oscilloscope to the input signal(pin 3) and CH_B to the output (pin 6) of the comparator. 10. Tune the 1kΩ potentiometer by observing the rectangular wave until you get a perfect square wave (with the amount of positive time being approximately the same as the amount of the negative time) as shown in Figure 4. (~50% duty cycle) Figure 4: Comparator input and output waveforms Place Your Scope Display Here
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11. Measure the DC voltage at pin 2 using a voltage probe. The measured voltage is ____________600uv________________ 12. While measuring the DC voltage at pin 2, tune the 1kΩ potentiometer so that the DC voltage value begins to go more negative . What effect does it have on the comparator output? Hint: Comment on the output duty cycle and the trigger level. Sample scope display below. Write your observations below. As the DC voltage on pin 2 is turned more negative, the duty cycle diminishes the negative side, and the output voltage becomes more negative.
Place Your Scope Display Here 13. While measuring the DC voltage at pin 2, tune the 1kΩ potentiometer so that the DC voltage value begins to go more positive. What effect does it have on the comparator output? Hint: Comment on the output duty cycle and the trigger level. Sample scope display below. Write your observations below. As the voltage rises or become more positive the output voltage also becomes more positive while the output duty cycle decreases on the positive cycle.
Place Your Scope Display Here
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14. Now modify the circuit by reversing the inputs such that, the input signal connects to pin 2 and the potentiometer wiper connects to pin 3. Figure 5: Inverted Comparator Place Your Schematic Here
15. The observed phase shift between the input and output signal is __180_______ degrees. Place Your Scope Display Here
*********End of the experiment *********
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