ARRL Technician Practice Exam

What are the three electrodes of a PNP or NPN transistor?

1. Emitter, base, and collector

2. Source, drain, and gate

3. Positive, negative, and base

4. Anode, cathode, and base

The correct answer is: Emitter, base, and collector

A transistor, whether it's of the PNP or NPN type, consists of three essential components known as electrodes: the emitter, base, and collector. These electrodes play crucial roles in the operation of the transistor. The emitter is responsible for injecting charge carriers (electrons in NPN transistors and holes in PNP transistors) into the base region. The base acts as a control terminal; its width is very thin compared to the other two regions, enabling it to control the flow of charge carriers between the emitter and the collector. Lastly, the collector captures the charge carriers flowing through the base, allowing them to complete the circuit and effectively amplify electrical signals. Understanding these components is fundamental for grasping how transistors function in electronic circuits, particularly in amplification and switching applications. The other choices refer to components associated with different types of devices, such as field-effect transistors (FETs) or diodes, which do not apply to the basic construction of bipolar junction transistors (BJTs) like PNP and NPN.