Semiconductors-Basic Transistor Electronics-Lecture Slides, Slides of Basic Electronics

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Basic Electronic Engineering

Lecture 1

Types of Materials

• Conductors
  • Materials that offer low resistance to electric current
• Semi conductors
  • Materials that have a value of resistance between that of a conductor and an insulator
• Insulators
  • Material that offers high resistance to the flow of current

Covalent Bonds

Types of Semiconductors

• Semiconductors do not conduct well in intrinsic form
• Semiconductors are modified by adding impurity atoms to increase conductivity
• Two types of extrinsic semiconductors exists
  • n-type Semiconductors
  • p-type Semiconductors

n-type semiconductors

p-type semiconductors

• Trivalent impurity atoms are added to intrinsic silicon or germanium
• Impurities include Boron, Indium and Gallium
• Holes are the majority carriers in p-type semiconductor materials
• Electrons are minority carriers

Majority and Minority Carriers

p-n junction Diode

• Diode is formed by joining p-type and n-type materials together
• A diode is a unidirectional device
• There is no net charge on the device as the number of electrons are equal to the number of protons

Diode

• Depletion Region
  • Charges move across the junction to combine leaving behind a region void of charges

Diode

• Barrier potential
  • Positive and negative charge around the junction forms an electric field
  • This electric field acts as a barrier for further electrons from n-region to move to p-region
  • Barrier potential of silicon is 0.7 V and barrier potential of germanium is 0.3 V at room temperature