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Electronic Devices and Circuits - Introduction

Semiconductor, Conductor, Energy Gap

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Electronic Devices and Circuits - Introduction

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  1. EC3353 – Electronic Devices and Circuits Prepared By Dr.C.GOKUL Professor/ECE

  2. Basics

  3. Electronics? • Electronic Devices? - Components • Electronic Circuits? • Active Elements? • Passive Elements?

  4. Conductor?

  5. Conductor? • 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.

  6. Semiconductor =>Semi + ConductorEx: Si

  7. Semiconductor • Siliconis 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.

  8. 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.

  9. Silicon Crystal

  10. Insulator?How the conductivity in Insulator?

  11. Semiconductors, Conductors, & Insulators Energy Bands • 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.

  12. Semiconductor -> Classifications • Intrinsic Semiconductors • Extrinsic Semiconductors • n-type semiconductor • p-type semiconductor

  13. IntrinsicSemiconductors • 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 +Vebattery terminal. Two Types of Flow: • Flow of free electrons through larger orbits (conduction band). • Flow of holes through smaller orbits (valence band).

  14. DOPING A SEMICONDUCTOR ?Why Doping?Extrinsic Semiconductor => Intrinsic Semiconductor + Doping=> Doped Semiconductor How the conductivity after doping?

  15. N-type and P-type Semiconductors • 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 • Trivalent Impurities: • Aluminum (Al) • Gallium (Ga) • Boron (B) • Indium (In) • Pentavalent Impurites: • Phosphorus (P) • Arsenic (As) • Antimony (Sb) • Bismuth (Bi)

  16. Antimony (Sb) - Pentavalent ImpurityBoron (B) - Trivalent Impurity

  17. References • CircuitBread – YouTube Channel • ALL ABOUT ELECTRONICS– YouTube Channel • The science works – YouTube Channel • Electrical4U – YouTube Channel

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