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Electronic workshop. Lecture-7 Diodes and Transistors. Dr. Imtiaz Hussain email: [email protected] 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
Electronic workshop

Lecture-7

Diodes and Transistors

Dr. Imtiaz Hussain

email: [email protected]

URL :http://imtiazhussainkalwar.weebly.com/


Semiconductor diodes
Semiconductor Diodes

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


Si

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Si

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Si

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Si

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Si

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Si

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Si

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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.


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.

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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.

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Si

+4

Si

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Si

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Si

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Si

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Si

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Si

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Si

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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.



Diode biasing

Short Circuit

Open Circuit

Diode Biasing

Forward Biased Diode

Reverse Biased Diode


Light emitting diode led
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.



Task 1
Task#1

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


Task 2
Task#2

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


Transistor
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)


BJT

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


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



End of lecture 7

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http://imtiazhussainkalwar.weebly.com/

End of Lecture-7


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