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Electronic workshop

Electronic workshop. Lecture-7 Diodes and Transistors. Dr. Imtiaz Hussain email: imtiaz.hussain@faculty.muet.edu.pk URL : http://imtiazhussainkalwar.weebly.com/. Semiconductor Diodes. Diode is constructed by fusing two different types of doped semiconductors (P-type and N-type) together. .

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Electronic workshop

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  1. Electronic workshop Lecture-7 Diodes and Transistors Dr. Imtiaz Hussain email: imtiaz.hussain@faculty.muet.edu.pk URL :http://imtiazhussainkalwar.weebly.com/

  2. Semiconductor Diodes • Diode is constructed by fusing two different types of doped semiconductors (P-type and N-type) together.

  3. Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 What Are Diodes Made Out Of? • Silicon (Si) and Germanium (Ge) are the two most common single elements that are used to make Diodes. • Silicon and Germanium are both group 4 elements, meaning they have 4 valence electrons. Their structure allows them to grow in a shape called the diamond lattice. • In diamond lattice lattice, each atom shares its valence electrons with its four closest neighbors. • This sharing of electrons is what ultimately allows diodes to be build. When dopants from groups 3 or 5 (in most cases) are added to Si or Geit changes the properties of the material so we are able to make the P- and N-type materials that become the diode.

  4. N-Type Material • When extra valence electrons are introduced into a material such as silicon an n-type material is produced. • The extra valence electrons are introduced by putting impurities or dopants into the silicon. • The dopants used to create an n-type material are Group V elements. The most commonly used dopants from Group V are arsenic, antimony and phosphorus. • The 2D diagram to the left shows the extra electron that will be present when a Group V dopant is introduced to a material such as silicon. This extra electron is very mobile. +4 +4 +4 +4 +5 +4 +4 +4 +4

  5. P-Type Material • P-type material is produced when the dopant that is introduced is from Group III. • Group III elements have only 3 valence electrons and therefore there is an electron missing. • This creates a hole (h+), or a positive charge that can move around in the material. Commonly used Group III dopants are aluminum, boron, and gallium. • The 2D diagram to the left shows the hole that will be present when a Group III dopant is introduced to a material such as silicon. This hole is quite mobile in the same way the extra electron is mobile in a n-type material. +4 +4 +4 +4 +3 +4 +4 +4 +4

  6. Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 Si +4 What Are Diodes Made Out Of? • Silicon (Si) and Germanium (Ge) are the two most common single elements that are used to make Diodes. Gallium is a group 3 element while Arsenide is a group 5 element. When put together as a compound, GaAs creates a zincblend lattice structure. • In zincblendlattice, each atom shares its valence electrons with its four closest neighbors. This sharing of electrons is what ultimately allows diodes to be build. When dopants from groups 3 or 5 (in most cases) are added to Si, Ge or GaAs it changes the properties of the material so we are able to make the P- and N-type materials that become the diode.

  7. Diode Terminals

  8. Short Circuit Open Circuit Diode Biasing Forward Biased Diode Reverse Biased Diode

  9. Light Emitting Diode (LED) • A compound that is commonly used for LEDs construction is Gallium Arsenide (GaAs), because of it’s large bandgap. • Gallium is a group 3 element while Arsenide is a group 5 element. • When put together as a compound, GaAs creates a zincblend lattice structure.

  10. Light Emitting Diode (LED)

  11. Task#1 • Take few diodes and check it using multimeter’s continuity function and fill in the following table.

  12. Task#2 • Take few LEDs and check it using the same method as task#1 and fill in the following table.

  13. Transistor • A transistor is a 3 terminal device that is used in a variety of applications such as amplification and switching. • There are two types of transistors categorized according to their construction: • Bipolar Junction Transistor (BJT) • Field Effect Transistor (FET)

  14. BJT • The Bipolar Junction Transistor (BJT) comes in two flavors

  15. FET • It is a two layer three terminal device made up of two pieces of semiconductors. • Like the BJT, this comes in two flavors too

  16. Task#3

  17. To download this lecture visit http://imtiazhussainkalwar.weebly.com/ End of Lecture-7

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