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. 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 + Conductor Ex: Si

7. 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.

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. 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.

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

13. 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).

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 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

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

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