Performance-Based Assessments for Digital Circuit Competencies

Here, I let students choose appropriate values for R_pulldown and R_limit, rather than specify them as given conditions.

I recommend the use of the LM339 comparator for this circuit.

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.

The choice of diodes is not critical in a circuit where the inputs come from manually actuated switches. Neither is the choice of resistor sizes (10 kΩ) works just fine, especially when the only thing loading the output is the student’s logic probe or voltmeter.