Transistors

Transistors are semiconductor devices used to amplify or switch electronic signals. The main types of transistors are:

1. Bipolar Junction Transistor (BJT): 

Comprises three layers which are emitter, base, and collector. It can be NPN or PNP type and operates by using small current input at the base to control larger current flow between collector and emitter.

2. Field-Effect Transistor (FET): 

Controls current with an electric field rather than a direct current input. It includes:

(i) Junction FET (JFET): Uses a junction between semiconductor materials to control current.

(ii) Metal-Oxide-Semiconductor FET (MOSFET): The most common FET type, used widely in digital circuits. It has a gate, drain, and source.

3. Darlington Transistor: 

A pair of BJTs combined to provide higher current gain.

4. Insulated-Gate Bipolar Transistor (IGBT): 

Combines the high efficiency of a MOSFET with the high current capacity of a BJT, commonly used in power electronics.

Each type of transistor is suited for different applications, depending on the need for amplification, switching, and power handling.