Lab 1: Superposition, Thevenin's Equivalent Circuit, and LTSpice Review

Name: Audra Benally

Email: albenally1@fortlewis.edu

1. Title: Review Superposition, Thevenin's Equivalent Circuit, and LTSpice

2. Introduction: The purpose of this lab is to review the superposition and thevenin equivalent methods to analyze circuits. The analysis was completed via hand calculations and the calculated values were verified with LTSpice simulations. LTSpice code was also reviewed by using the separate .txt file technique. All the calculated values were found and displayed in Figures 2, 4, and 5.

3. Materials and Methods:

Materials:

- Pencil and Paper

- Computer

- LTSpice Software

Methods:

Two separate circuits were analyzed in this lab using the superposition and thevenin's equivalent methods. Task 1 called for the superposition method. Hand calculation are shown in Figure 1. The task 1 spice code and circuit values can be seen in Figure 2. I decided to use the .op spice command for task 1 to get an easy look at all the current and voltage values. Task 2 had us use the thevenin's equivalent method to analyze the given circuit. Task 2 hand calculation can be seen in Figure 3. Task 2 spice code (for original circuit) and simulation in shown in Figure 4. One cursor was used to show the maximum voltage output in Figure 4. Two cursors were manipulated to show the time delay from the simulation in Figure 5.

4. Results:

Figure 1. Hand calculations using superposition to solve the circuit values.

Figure 2. LTSpice code and .op current and voltage simulation values.

Figure 3. Hand calculations calculating the Thevenin's equivalent circuit to find the time delay (td).

Figure 4, LTSpice code of original circuit and simulation results. The highlighted value is the Eth value in the hand calculations, and the value of the full Vout charge.

Figure 5. Task 2 simulation with two cursors measuring the time delay (highlighted).

5. Discussion

The purpose of this lab was to review important methods that we will use to analyze upcoming circuits in this semester. This lab was a great refresher on methods that I had only vaguely remembered. The provided videos were a very helpful source for the hand calculations. All the calculations were verified in the simulations and shown in figures 2, 4, and 5. The only issue I had was tweaking the spice code for task 2. The values for the PULSE() function took a little while to find in order to show the time delay in action. The calculation of the time delay was helpful with this problem. Overall, I would call this lab successful and a good start for the lab portion of this class!