ENGR338 2020 Spring
Lab 1
John Hitti
jdhitti@fortlewis.edu

Lab 1:
In this lab we were tasked with reviewing the topics of Superposition, Thevenin's Equivalent Circuit, RC time delay, and the schematic simulation program LT Spice.


Task 1:
In task 1 we used the superposition theorem to calculate all the voltages and currents in the following circuit:

Figure 1. Electrical circuit solved in Task 1


Figure 2. These hand calculations used superposition to solve for the voltages at all the notes and currents through each resistor.



Figure 3. These calculations were then verified using LT Spice. Graphed above is the voltage at all nodes and the current through each resistor.



Task 2:
In task 2 we converted the circuit below to its Thevenin's equivalent circuit to solve the time delay of the 4nF capacitor.

Figure 4. Electrical circuit solved in Task 2


Figure 5. Hand calculations were used to solve for both the equivalent Resistance and the equivalent voltage.
Once the Thevenin's equivalent circuit was calculated the resistance could be used to calculate the time constant for the 4nF capacitor. This could then be used to estimate an approximate rising and falling time of 32 micro-seconds.



Figure 6. The given calculations were then verified in LT Spice.
LT Spice was then used to verify our calculations. Given a voltage pulse with a 100 microsecond period the capacitor produced a rise/fall time of approximately 32 microseconds.


Discussion:
This lab was an excellent review to the topics of Superposition, Thevenin's Equivalent circuit, RC time delay, and the schematic simulation program LT Spice. After completing this lab I feel more confident in my ability to use these tools to progress in the course.