diodes-1

  • A Journey to Electronics: Semiconductors and Diodes

  • Speaker & Author: Dr. Budditha Hettige, BSc, MPhil, PhD

Contents Overview

  • Semiconductors: Defined and categorized

  • Doping: Techniques for altering semiconductor properties

    • N-Type Doping: Adding impurities to create excess electrons

    • P-Type Doping: Creating holes in the semiconductor lattice

  • PN-Junction: Structure and significance in diodes

  • Applications of PN Junctions: Various electronic components

  • Diodes: Usage and characteristics

  • Rectifier Diodes: Key features and functionalities

  • Different Types of Diodes: Based on application and structure

  • Zener Diodes: Voltage regulation properties

  • LED Technology: Overview, working principle, and applications

  • Photodiodes and Solar Cells: Conversion of light to electrical energy

Semiconductors

  • Categorization:

    • Conductors: High free electron density (e.g., copper, gold)

    • Insulators: Low free electron density (e.g., rubber, glass)

    • Semiconductors: Moderate conductivity, can be altered by doping (e.g., Silicon, Germanium).

Doping Methods

  • Definition: The addition of impurities to modify electrical properties

    • N-Type Doping: Utilizes pentavalent elements (e.g., Phosphorus) to add extra electrons.

    • P-Type Doping: Involves trivalent elements (e.g., Boron) creating electron 'holes' facilitating positive charge flow.

PN-Junction

  • Formation: A boundary between N-type and P-type semiconductors.

  • Key Concepts:

    • Depletion Region: Area with no free charge carriers resulting from charge diffusion across the junction.

    • Electric Field: Developed due to charge separation, opposing further carrier diffusion.

    • Forward Bias: Application of positive voltage allows current; reduces potential barrier.

    • Reverse Bias: Increases potential barrier; blocks current flow.

Applications of PN-Junction

  • Electronic Components: Basis for diodes, LEDs, and solar cells.

Diodes

  • Definition: A two-terminal device allowing current in one direction only.

  • Types:

    • Rectifier Diodes: Convert AC to DC.

    • Zener Diodes: Regulate voltage, have specified breakdown voltage.

    • Schottky Diodes: Feature low forward voltage drop.

    • LEDs: Convert electrical energy into light.

Characteristics of Diodes

  • Forward Voltage Drop: Typically 0.6 to 0.7 volts for silicon diodes.

  • Reverse Breakdown Voltage: Critical point where diode conducts in reverse.

Rectifiers

  • Half-Wave Rectifier: Converts one half-cycle of AC; lower efficiency.

    • Ripple Factor: Measure of voltage fluctuations; higher in half-wave rectifiers.

  • Full-Wave Rectifier: Utilizes both halves of AC; produces smoother DC output.

  • Bridge Rectifier: Uses four diodes; delivers full-wave rectified output without a center-tap.

Zener Diodes

  • Working Principle: Maintain a constant voltage in reverse bias operation; essential for voltage regulation.

  • Characteristics:

    • Zener Voltage: The specified voltage at which breakdown occurs.

Light-Emitting Diodes (LEDs)

  • Definition: Semiconductor devices that emit light upon electrical input.

  • Working Principle: Based on electroluminescence; color depends on semiconductor bandgap.

    • Types: DIP, SMD (Surface Mounted Diode), and COB (Chip on Board) LEDs.

    • Advantages: Energy-efficient, long lifespan, durable, and versatile in various applications.

Solar Cells

  • Definition: Converts sunlight into electricity through the photovoltaic effect.

    • Key Features:

      • P-N Junction: Creates electric field aiding charge movement.

  • Advantages: Renewable energy source; environmentally friendly.

  • Disadvantages: Performance affected by weather conditions; initial installation costs.

Photodiodes

  • Functionality: Converts light into electrical current; crucial in optical communication and sensing applications.

  • Applications: Used in cameras, smoke detectors, and as light sensors.