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ELECTRONICS, RESOURCES:, download , Intrinsic-Semiconductors , …
ELECTRONICS
Semiconductors
They are materials which have a conductivity between conductors (generally metals) and nonconductors or insulators (such as most ceramics). Semiconductors can be pure elements, such as silicon or germanium, or compounds such as gallium arsenide or cadmium selenide. There are two types:
Intrinsic semiconductors: An intrinsic semiconductor is a pure semiconductor without any significant dopant species present. The number of charge carriers is therefore determined by the properties of the material itself instead of the amount of impurities.
Extrinsic semiconductors:
Extrinsic semiconductors are semiconductors that are doped with specific impurities. While adding impurities, a small amount of suitable impurity is added to pure material, increasing its conductivity by many times. Extrinsic semiconductors are also called impurity semiconductors or doped semiconductors
Diodes
A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance). It is formed by fusing P-type and N-type extrinsic semiconductors hence also called as PN-junction. There are 3 main types of diodes:
Light Emitting Diode (LED): The potential barrier between p and n sides is such that when an electron combines with a hole during forward bias conduction, a photon of visible light is emitted.
Photo Diode: A photodiode is a semiconductor p-n junction device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode.
Photo-Voltaic Cell: A photodiode is a semiconductor p-n junction device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode.
Transistors
A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. Transistors are one of the basic building blocks of modern electronics. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. It has one type of semiconductor sandwiched between other type of semiconductor. The three terminals are named as Emitter, Base and collector. The emitter-base junction is forward biased and collector base junction is reverse biased. Bipolar Junction Transistors (BJTs) has two types:
1) NPN Transistor: The NPN transistor is made up of three semiconductor layers: one p-type semiconductor layer and two n-type semiconductor layers. The p-type semiconductor layer is sandwiched between two n-type semiconductor layers.
2) PNP Transistor: A PNP transistor is a bipolar junction transistor constructed by sandwiching an N-type semiconductor between two P-type semiconductors. A PNP transistor has three terminals – a Collector (C), Emitter (E) and Base (B). The PNP transistor behaves like two PN junctions diodes connected back to back.
Doping : It is the process by which impurity
is added to an intrinsic semiconductor to transform it into extrinsic semiconductor in order to improve conductance. Depending on the type of impurity
added, two types of extrinsic semiconductors are
produced as a result of doping:
1) N-type semiconductor: This type of semiconductor is formed when a 'pentavalent impurity' is added to an intrinsic semiconductor. The majority charge carriers in N-type are free electrons and minority charge carriers are holes.
2) P-type semiconductor: This type is formed when a 'trivalent impurity' is added to an intrinsic semiconductor. The majority charge carriers in P-type are holes and minority charge carriers are free electrons.
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