Britannica Sources used in this answer

What are the emitter, base, and collector terminals in a bipolar transistor?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

NMOS transistorNegative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors. — transistor NMOS transistor
Negative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors.

In a bipolar transistor, the three terminals—the emitter, base, and collector—each perform a specific role in the device's operation:1

Emitter: This terminal is responsible for injecting or emitting charge carriers (electrons or holes) into the base region. It is typically heavily doped to facilitate this injection process.1
Base: Positioned as a narrow central region between the emitter and collector, the base acts as a control terminal. A small change in input voltage or current at the base regulates the flow of charge carriers from the emitter to the collector.12
Collector: This terminal collects the charge carriers that have been injected from the emitter and successfully passed through the base region. The collector-base junction is typically reverse-biased, allowing it to effectively gather these carriers.12

Together, these terminals allow the transistor to function as an amplifier or switch by controlling a large output current with a relatively small input signal at the base.12