Basic Characteristics of a Bipolar Junction Transistor

In this video, we dive into the Basic Characteristics of Bipolar Junction Transistor (BJT), a key topic in Analog Electronics. A BJT is a semiconductor device that amplifies or switches electrical signals, commonly used in various electronic circuits. We’ll explore its structure, operation, and characteristics, including input-output curves, current gain (β), and saturation & cutoff regions. 

A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current flowing between the terminals, making the device capable of amplification or switching.

BJTs use two p–n junctions between two semiconductor types, n-type and p-type, which are regions in a single crystal of material. The p–n junctions are formed by diffusing impurities into the semiconductor material to create regions with different electrical properties. The n-type region has an excess of electrons, while the p-type region has a deficiency of electrons.

When a voltage is applied to the BJT, it creates a current that flows through the p–n junctions. The current through the junctions is controlled by the amount of voltage applied, and by the type of semiconductor material used to make the junctions.

BJTs can be used in a variety of electronic circuits, including amplifiers, switches, and oscillators. They are also used in many common devices, such as computers, televisions, and mobile phones.