What is the primary electrical characteristic of a bipolar transistor?

A bipolar transistor is characterized primarily by its ability to use both electrons and holes as charge carriers. This duality of charge carriers is what distinguishes bipolar transistors from unipolar transistors, which rely solely on one type of charge carrier, either electrons or holes.

In a bipolar transistor, there are two types of charge carriers at play: electrons, which are negatively charged, and holes, which can be thought of as positively charged vacancies left by electrons. This mechanism allows bipolar transistors to amplify current effectively and function as switches, making them versatile components in various electronic applications.

Understanding this characteristic is crucial, as it relates to the fundamental operation of the transistor, including its current-voltage relationships, switching characteristics, and gain. This dual carrier operation is also why the term "bipolar" is used, highlighting the involvement of both types of charges in its functioning.