Performance-Based Assessments for Semiconductor Circuit Competencies

Being able to design a circuit using a BJT as a switch is a valuable skill for technicians and engineers alike to have. The circuit shown in this question is not the only possibility, but it is the simplest.

Remind your students that the equation for calculating BJT power dissipation is as follows:

$$P_Q = I_C(V_{CE} + \frac{V_{BE}}{\beta})$$

An extension of this exercise is to incorporate troubleshooting questions. Whether using this exercise as a performance assessment or simply as a concept-building lab, you might want to follow up your students’ results by asking them to predict the consequences of certain circuit faults.

Being able to design a circuit using a BJT as a switch is a valuable skill for technicians and engineers alike to have.

An extension of this exercise is to incorporate troubleshooting questions. Whether using this exercise as a performance assessment or simply as a concept-building lab, you might want to follow up your students’ results by asking them to predict the consequences of certain circuit faults.

Use a variable-voltage, regulated power supply to supply any amount of DC voltage below 30 volts.

I highly recommend specifying a large value for R_series and/or a high-wattage rated transistor and variable load resistor, so that students do not dissipate excessive power at either the transistor or the load as they test for R_load (min). Do not use a decade resistance box for R_load unless you have made sure its power dissipation will not be exceeded under any circuit condition!

An extension of this exercise is to incorporate troubleshooting questions. Whether using this exercise as a performance assessment or simply as a concept-building lab, you might want to follow up your students’ results by asking them to predict the consequences of certain circuit faults.