Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Electronics and Communication → Semiconductors ↓


Diodes and their applications


Diodes are fundamental components in the fields of electronics and communications. They are one of the simplest semiconductor devices, but they are incredibly important due to their unique ability to allow current to flow in only one direction. In this exploration, we will take a deep dive into what diodes are, how they work, and their various applications.

Understanding semiconductors

To understand diodes, it is important to first understand semiconductors. Semiconductors are materials whose electrical conductivity lies between that of a conductor such as copper and an insulator such as glass. This characteristic allows them to be used in electronic components.

The most commonly used semiconductor material is silicon. Semiconductors are unique because their conductivity can be changed by adding impurities in a process called "doping." This is how diodes and other semiconductor devices are made.

What is a diode?

A diode is a semiconductor device that allows current to flow in only one direction. It has two terminals: anode and cathode. The symbol for a diode is a triangle with a line pointing up:

In this symbol, the triangle represents the anode and the line represents the cathode. Current flows from the anode to the cathode, but not the other way around. This one-way property makes diodes useful for converting alternating current (AC) to direct current (DC), among other applications.

How do diodes work?

Pn junction

The main principle of a diode is the PN junction. The PN junction is formed when a P-type and N-type semiconductor material are joined together.

  • P-type: This semiconductor material has an abundance of "holes" or positive charge carriers. It is created by doping the semiconductor material with elements such as boron.
  • N-type: It has an abundance of electrons or negative charge carriers. It is made by adding elements like phosphorus.

Formation of depletion region

When P-type and N-type materials are put together, electrons from the N-type region diffuse into the P-type region and recombine with holes. This creates a region around the junction where there are no charge carriers, known as the depletion region.

The formation of this region creates an electric field that opposes the forward flow of electrons, creating a balance point. Only under certain conditions (such as applying an external voltage) do electrons and holes flow across the junction.

Forward bias and backward bias

The operation of a diode depends greatly on how the voltage is applied across it. This leads to two scenarios:

  • Forward bias: In this case, a positive voltage is applied to the anode, and a negative voltage is applied to the cathode. This reduces the resistance of the depletion region, allowing current to flow through the diode. The diode is a conductor.
  • Reverse bias: Here, a positive voltage is applied to the cathode, and a negative voltage is applied to the anode. This increases the resistance of the depletion region, preventing current from flowing through the diode. The diode is a non-conductor.
P-type N-type depletion region

Applications of diode

Avoidance

A primary application of diodes is to convert AC to DC, known as rectification. This is done using a rectifier circuit.

Half-wave rectifier

In a half-wave rectifier, an AC input is applied to a diode, which allows only one half of the AC waveform to pass through, blocking the other half. This produces a pulsating DC output.

Using a single diode, this simple circuit can be created, where the input AC sinusoidal wave is converted into a series of positive waves only. However, the power lost due to the blocked negative half is a disadvantage.

        AC Input ----|>|---- Load (-) Diode
        AC Input ----|>|---- Load (-) Diode

Full-wave rectifier

A full-wave rectifier uses more diodes to convert the entire AC wave to DC. This can be done using:

  • Center-tapped full-wave rectifier: Uses a center-tapped transformer and two diodes.
  • Bridge rectifier: Uses four diodes arranged in a bridge configuration to achieve full-wave rectification without a center-tapped transformer.

Function of bridge rectifier

In a bridge rectifier, four diodes are connected as shown below to convert AC to DC more effectively:

During the positive half of the AC cycle, two diodes conduct, and during the negative half, the other two conduct, allowing current to pass through the load in only one direction. This results in a smooth DC output.

Signal demodulation

Diodes are also used in demodulating AM signals. AM stands for amplitude modulation, a technique used in transmitting information via radio waves. At the receiver, the diode demodulator extracts the audio or original information signal from the modulated carrier wave.

Voltage regulation

Diodes known as Zener diodes are used to maintain a constant voltage level. When they operate in reverse bias, Zener diodes can allow current to flow backwards if the Zener breakdown voltage is reached, thereby stabilizing the voltage supplied to other components.

Zener diode

Zener diodes are special types of diodes designed to make current flow "backwards" when a certain set reverse voltage (known as the Zener voltage) is reached. This makes them extremely useful for voltage regulation in power supply circuits.

Other applications

  • Clamping circuit: Diodes are used to shift the level of the wave to the desired value. It is used in TV and other signal processing circuits.
  • Clipping circuits: Diodes can clip portions of the signal voltage above and below certain levels, allowing signal distortions to be corrected.
  • Switching: Used as a switch in digital logic gates that allows or restricts the flow of binary signals (0 and 1).
  • Protection circuits: Diodes are used to prevent damage to circuits caused by reverse polarity voltage, acting as a one-way valve for electricity.

Conclusion

Diodes are a versatile and vital component in modern electronics, serving many purposes from rectification to voltage regulation and signal demodulation. Their ability to control the direction of current flow makes them an essential building block in the design of complex electronic devices. Understanding their function and applications helps us appreciate their vital role in the electronics that power our world every day.


Grade 10 → 7.1.2


U
username
0%
completed in Grade 10

← Prev (7.1.1)
Conductors, Insulators and Semiconductors
Next (7.1.3) →
Transistors and Logic Gates

Comments 



Diodes and their applications

https://www.physicsflow.com/g10/7.1.2?pfal=en