Day 6 - Mesh Analysis and Transistors

Topics Discussed

On day 6 of the ENGR 44 course, we further discussed the advantages of mesh analysis. We continued to do example problems to reiterate how to apply these techniques to circuit analysis (Fig. 1). Additionally, we also developed a new skill using mesh analysis in which we could create a matrix by simply looking at the circuits elements (Fig. 2).

Fig. 1

Fig. 2

We were also introduced to transistors and the difference between NPN transistors and PNP transistors, and how each differ in terms of the current they direct. We discussed techniques of how to analyze circuits which contained a transistor element, and we solved group practice problems (Fig. 3). We also performed a demo with the analog discovery system in which a current or voltage could be provided at an alternating rate. We formed graphs from the information received (Fig. 4 & 5).

Fig. 3

Fig. 4

Fig. 5

Mesh Analysis 2 Lab

In this lab, we sought to use mesh analysis to predict the values of voltage and current across certain elements within the circuit. By using the analog discovery device, we should be able to build our theoretical circuit and test to see if mesh analysis yields us the true values we will measure in the lab. 

To begin, we first drew a diagram of the circuit and used mesh analysis to find the voltage across our 6.8k ohm resistor, and current through our 10k ohm resistor (Fig. 6).

Fig. 6

Once we found these values we built our circuit (Fig. 7). We measured our values for current and voltage across the desired elements and recorded our data as well as percent error. (Fig. 8)

Fig. 7

Fig. 8

Summary

In this lab, we were able to verify the true application of mesh analysis on an actual circuit. Our value for voltage had only a 1.6% error, while our current had a 21.7% Error. The largest source of error accounted in the current may be in part due to the real values of our resistors. Our 4.7k ohm resistor had the biggest difference than what we had intended, and this may have had a large impact on how much current went through the 10k ohm resistor. Overall, our lab successfully verified the usefulness of mesh analysis.