Lab 2 Write Up

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Apr 3, 2024

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University of Florida EEL3111C – Circuits 1 Santiago Tovar Electrical & Computer Engineering Dept. Lab 2: LTSpice Page 1/2 Revision: 0 February 5 th , 2024 INTRODUCTION In this lab, we are mainly learning how to use LTSpice. In the first part, we will learn how to draw a basic circuit and use parameters to change the value of resistors. Next, we are going to learn more parameters to calculate the voltage at a node in its max and min value. Lastly, we are going to check the prices of different resistors depending on their tolerance. DISCUSSION 2.5.1 Equivalent Resistance In this part of the lab, we must calculate the equivalent resistance of an R-2R ladder circuit. First using 470 as the value for the resistors, then a second time using 500. Next, calculate by hand the equivalent resistance for both values. The equivalent resistance using 470 ohms resistors is 489.7 ohms. The equivalent resistance using 500 ohms resistors is 500 ohms. 2.5.2 Monte Carlo with Different Tolerances In this part, we have to test the circuit already done in the prelab with different values for the tolerance. Then table the voltage ranges at each node. Tolerance Vmax(A) Vmin(A) Vmax(B) Vmin(B) Vmax(C) Vmin(C) Vmax(D) Vmin(D) 1% 4.41 4.39 3.15 3.12 1.88 1.84 0.61 0.59 0.1% 4.40 4.40 3.14 3.13 1.87 1.86 0.60 0.59 0.05% 4.40 4.40 3.14 3.13 1,87 1.86 0.60 0.60 0.01% 4.40 4.40 3.13 3.13 1.87 1.87 0.60 0.60 0.005% 4.40 4.40 3.13 3.13 1.87 1.87 0.60 0.60 Table 2.5.2: min and max voltages at each node

University of Florida EEL3111C – Circuits 1 Santiago Tovar Electrical & Computer Engineering Dept. Lab 2: LTSpice Page 2/2 Revision: 0 February 5 th , 2024 2.5.3 Resistor Costs In this part of the lab we have to search resistors with different tolerances and compare them by maximum and minimum unit cost. If out of stock just write that instead of the price. Tolerance Max Price Min Price 5% 6.07$ 0.007$ 1% 26.5$ 0.009$ 0.1% 25.27$ 0.07$ 0.05% 30.5$ 2.7$ 0.01% 34.8$ 6.54$ 0.005% Out of Stock Out of Stock Table 2.5.3: Max and min prices for each resistor depending on tolerance. Discuss the effects of resistor variation, the effect it had on the resistor ladder and its associated node voltages, and the cost of resistors with a tighter tolerance. Mention the two equivalent resistor values only briefly. The resistor variation also affects the node voltages. This is because as the resistor increases its value, the voltage at that branch decreases, meaning that voltage depends also on the resistor value. We can see this in the first part when calculating the equivalent resistance of 489 and 500 ohms. Also, as the tolerance increases (e.g. from 1% to 0.005%) the min and max voltage at a node start to be closer and closer. CONCLUSION After this lab I learned the impact of the resistors in the circuit. Meaning that I have learned how the circuit is affected depending on the resistor value and tolerance. Making the min and max voltages be almost the same at the highest tolerance (0.005%).

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