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Published byGokul C Modified 10 months ago
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EC3353 – Electronic Devices and Circuits Prepared By Dr.C.GOKUL Professor/ECE
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Basics
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Electronics? Electronic Devices? - Components Electronic Circuits? Active Elements? Passive Elements?
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Conductor?
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Copper atom => one electron in its outer orbit. This single electron can be easily dislodged from its atom => free electron. Good conductor => slightest voltage causes free electrons to flow from one atom to the next.
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Semiconductor =>Semi + Conductor Ex: Si
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Semiconductor Silicon is the most widely used semiconductor material. An isolated silicon atom has four electrons in its outer, or valence, orbit. Conductors => 1 valence electron Semiconductors => 4 valence electrons, Insulators => 8 valence electrons.
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SILICON CRYSTALS Each silicon atom in a crystal has its four valence electrons plus four more electrons that are shared by the neighboring atoms. Room temperature=> pure silicon crystal has only a few thermally produced free electrons and holes. The amount of time between the creation and recombination of a free electron and a hole is called the lifetime.
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Silicon Crystal
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Insulator? How the conductivity in Insulator?
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Energy Bands Semiconductors, Conductors, & Insulators Energy gap-the difference between the energy levels of any two orbital shells Band-another name for an orbital shell (valence shell=valence band) Conduction band –the band outside the valence shell where it has free electrons.
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Semiconductor -> Classifications Intrinsic Semiconductors Extrinsic Semiconductors n-type semiconductor p-type semiconductor
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Intrinsic Semiconductors Intrinsic semiconductor => pure semiconductor. When an external voltage is applied to the intrinsic semiconductor => Free electrons flow toward the +Ve battery terminal & Holes flow toward the +Ve battery terminal. Two Types of Flow: Flow of free electrons through larger orbits (conduction band). Flow of holes through smaller orbits (valence band).
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DOPING A SEMICONDUCTOR ? Why Doping? Extrinsic Semiconductor => Intrinsic Semiconductor + Doping => Doped Semiconductor How the conductivity after doping?
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N-type and P-type Semiconductors Trivalent Impurities: Aluminum (Al) Gallium (Ga) Boron (B) Indium (In) Pentavalent Impurites: Phosphorus (P) Arsenic (As) Antimony (Sb) Bismuth (Bi) 2 types of doping : -trivalent (3 valence e-) & -pentavalent (5 valence e-) p -type material – a semiconductor => trivalent impurities n -type material – a semiconductor => pentavalent impurities
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Antimony (Sb) - Pentavalent Impurity Boron (B) - Trivalent Impurity 16
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References CircuitBread – YouTube Channel ALL ABOUT ELECTRONICS– YouTube Channel The science works – YouTube Channel Electrical4U – YouTube Channel
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