bipolar transistor

electronics

Also known as: BJT, bipolar junction transistor

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Last updated

June 22, 2026

Quick Summary

A bipolar transistor is a crucial semiconductor device that utilizes both electrons and holes for electrical conduction, hence its name "bipolar". It functions by controlling a larger output current with a smaller input voltage applied to its base terminal.12

A bipolar transistor consists of three regions: the emitter, the base, and the collector. These regions are formed from p-type and n-type semiconductor materials, creating two p-n junctions. The emitter-base junction is forward-biased, allowing carriers (holes or electrons) to be injected into the base. The base-collector junction is reverse-biased. If the base region is sufficiently narrow, most injected carriers will pass through to the collector, enabling amplification.1

Bipolar transistors are known for their speed and are often used in high-frequency applications like radio-frequency integrated circuits. However, they consume more power than field-effect transistors (FETs), which offer better power efficiency.2

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