24. Transistor Selection

Question.4

You are building a circuit where a 12V cooling fan is permanently connected to the Positive (+) battery terminal. To turn the fan ON, you need a transistor to act as a "gate" that connects the fan's other wire to the Ground (-) terminal. You are looking at two options on Digi-Key:

Digi-Key PN: 2N3904-ND
Digi-Key PN: 2N3906-ND

Which Digi-Key part is the correct choice to sit between the fan and Ground to act as this "Low-Side" switch and why?

2N3906-ND: Because it is NPN and designed to switch the positive power.
2N3904-ND: Because it is NPN and it can "sink" the current from the fan into the Ground.
2N3906-ND : Because it PNP and it works better with high-speed fans.
2N3904-ND : Because it is PNP and prevents the fan from spinning backward.

Restart quiz!