When the electric current goes out from the transistor, then it is considered negative. If, however, the BJT is collector-based, it would be reverse biassed. If the BJT is emitter-based, then it would be forward-biassed. The collector region is the widest of the three regions, and it is where most of the charge carriers accumulate. The base is the sandwiched region, which is very thin, and the doping is light. The purpose of the heavily doped emitter region is to carry current carriers (either electrons or holes, depending upon the type of transistor) into the base. A typical BJT consists of three terminals – an emitter, a collector, and a base. Bipolar Junction Transistor ConstructionĪ bipolar junction transistor is the most widely used electrical component for the amplification of electrical signals. Holes and electrons are current carriers. An n-type (or a p-type) semiconducting material is sandwiched between two p-type (or two n-type) semiconducting materials. A junction transistor involves two p-n junctions. Transistors are broadly of two types – bipolar junction transistor (abbreviated as BJT) and field-effect transistor. The output power, current, and voltage of a transistor are strictly regulated by the input current. It acts as a gate (or as a switch) in electrical circuits.

It is nearly impossible to imagine a modern-day electrical circuit without a transistor. A transistor can be defined as a semiconducting electrical component that is majorly used for amplifying electrical signals over large distances.

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