03/10 - Lab 7: Mesh Analysis 2, and Lab 8: BJT Curve Tracer

Lab 7 - Mesh Analysis 2

In this lab, we analyzed and built a circuit containing multiple power sources. We were instructed to first analyze the circuit found in the lab manual, shown below:

Expected Values: V_1 = 5 V, V_2 = 0.24 V, and I_1 = 0.330 mA

Everycircuit confirms our prediction

After using a little bit of mesh analysis, but mostly everycircuit, we were able to find the values for I_1 and V_1. We then built the circuit using a solderless breadboard and the indicated resistors.

Closeup of the circuit design

The multimeter shows V_1 = 4.95 V, which is -1% from our predicted value of 5 V

Multimeter indicates V_2 = 0.24 V, which is exactly what was predicted (0% error)

The multimeter indicates I_1 = 0.320 mA, which is -3% from our predicted value

As the results of the lab show, our predicted values were very close to the actual values in the circuit. V_1 = 4.95 V (predicted 5 V ; 1% error), V_2 = 0.24 V (predicted 0.24 V ; 0% error), and 

I_1 = 0.321 mA (predicted 0.330 mA ; 3% error).

Lab 8 - BJT Curve Tracer

The purpose of this lab was to understand how transistors operate within a circuit. We were instructed to build the circuit depicted in the lab booklet, with each green box representing the lead to connect to the analog discovery box.

We had to create a custom waveform in order to achieve the "step" cycle going into W2, which was outlined in the lab manual. After setting up the waveform, we constructed the circuit on the wireless bread board:

Closeup of the curve tracer circuit

5 lines we were expected to see as outlined in the lab manual.

Because I suck at taking pictures of graphs, the values for I_C are not shown, however the horizontal markings start at 0 with the bottom line, and increase by 0.025 mA per line. Thus, the blue lines in the photograph land on approximately 0, 10, 20, 30, and 40 µA from bottom to top.

In Class Exercises:

1. Find IB , IC , and vo in the transistor circuit. Assume that the transistor operates in the active mode and that β = 50. Hint: recall that Vbe = 0.7 V in active mode.

Me doing ENGR 44 homework: