Transistor:
Transistor is a semiconductor device which is used to amplify the signals as well as in switching circuits. Generally transistor is made of solid material which contains three terminals such as emitter (E), Base (B) and Collector (C) for connections with other components in the circuit. Some transistors contains fourth terminal also i.e., substrate (S).
Figure: Transistor
Different types of transistors:
Figure: Transistor types
Bipolar Junction Transistor:
Figure: Bipolar Junction Transistor
A Bipolar Junction Transistor is a solid state device in which the current flow between two terminals (the collector and the emitter) is controlled by the amount of current that flows through a third terminal (the base).
NPN Transistor:
Figure: NPN Transistor
Here electrons move to the n+, and recombination of electrons will fill in the n++ type called doping of electrons. The majority charge carriers will go through n++ side. Then, this n++ is called Emiter, p is base and n+ is called collector.
PNP Transistor:
Figure: PNP Transistor
Here the doping of electrons does from emiter to the collector side. The electrons goes through the base and added to the collector side.
Field Effect Transistor (FET):
FET transistors have three terminals they are gate (G), Drain (D) and source (S). FET transistors are classified into Junction FET and Insulated Gate FET or MOSFET. For the connections in the circuit we also consider fourth terminal called base or substrate.
Figure: Field Effect Transistor
Junction FET:
JFETs can have an n-type or p-type channel, In the n-type, if the voltage applied to the gate is less than that applied to the source, the current will be reduced.Similarly in the p-type, if the voltage applied to the gate is greaterthan that applied to the source.
Figure: Junction Field Effect Transistor
MOSFET:
MOSFET abbrevates Metal Oxide Semiconductor Field Effect Transistor. The MOSFET is by far the most common transistor in digital circuits, as hundreds of thousands or millions of them may be included in a memory chip or microprocessor. Since MOSFETs can be made with either p-type or n-type semiconductors, complementary pairs of MOS transistors can be used to make switching circuits with very low power consumption.
Figure: MOSFET