The Base region is slightly doped and is thinner as compared to other regions. The PN junction that connects the base and emitter region is called the BE-junction while the junction connecting the base and collector is called the BC-junction. Two PN junction diodes are sandwiched together to form a BJT.

In other words, a BJT is formed by a 'sandwich' of extrinsic semiconductor materials placed back to back.

Hence they are widely used as amplifiers and switches in electronic equipment such as mobile phones, industrial control, television, and radio transmitters.Ī bipolar junction transistor is created by combining two doped semiconductor materials that are back-to-back. Another important application of BJT is switching circuits. The primary function of a BJT is to amplify current, which allows BJTs to be used as amplifiers. The three terminals of the BJT are the base, the collector, and the emitter. What is a BJT?Ī Bipolar Junction Transistor (BJT or BJT Transistor) is a three-terminal semiconductor device composed of two P-N junctions that can amplify or magnify a signal. In the case of a BJT, both electrons and holes could be used as charge carriers. If an N-type semiconductor is used the charge carriers are electrons while if a P-type semiconductor is used the charge carriers are holes. Unipolar transistors or Field Effect Transistors (FETs), as the name suggests use only one type of charge carrier, either electrons or holes depending on the type of semiconductor material used.

Pnp vs npn transistor