Question

What is the difference between a transistor and BJT?

Answer 1

Semiconductors are materials that transfer electricity between conductors (usually metals) and nonconductors (insulators) (such as most ceramics). Semiconductors are made up of pure elements like silicon and germanium, as well as compounds like gallium arsenide and cadmium selenide. Small quantities of impurities are introduced to pure semiconductors in a process called doping, which causes significant variations in the material's conductivity.

Complete step-by-step solution:
A transistor is a semiconductor device that is used to amplify or switch electrical impulses and power. Transistors are a fundamental component of contemporary electronics. It's made of semiconductor material and has at least three terminals for connecting to a circuit outside of it. The current through another pair of terminals is controlled by a voltage or current provided to one pair of transistor terminals. A transistor can magnify a signal because the regulated (output) power can be higher than the controlling (input) power. Some transistors are still packed separately nowadays, but many more are incorporated in integrated circuits.
Bipolar transistors get their name from the fact that they employ both majority and minority carriers to conduct. The bipolar junction transistor, the first mass-produced transistor, is made up of a thin layer of p-type semiconductor sandwiched between two n-type semiconductors (an n–p–n transistor) or a thin layer of n–type semiconductor sandwiched between two p–type semiconductors (a p–n–p transistor). A narrow area of semiconductor known as the base region separates two p–n junctions: a base-emitter junction and a base-collector junction, resulting in two p–n junctions.

Note: The three layers of semiconductor—emitter, base, and collector—are represented by the three terminals of a BJT. Because the currents at the emitter and collector may be controlled by a tiny base current, they are useful in amplifiers. The emitter-base junction is forward biassed (electrons and holes recombine at the junction), the base-collector junction is reverse biassed (electrons and holes form at and move away from the junction), and electrons are injected into the base region in a n–p–n transistor operating in the active region.