The Basics of Electronics

The Basics of Electronics

Electronics

Electronics is the branch of physics and technology concerned with the behaviour and movement of electrons.

Electron Emission

In metals, the electrons from the outermost orbit of an atom become free at room temperature. However, these free electrons cannot leave the surface of metals. To enable free electrons to leave the metal surface, external energy is required. Electron emission can be achieved by the following methods:

1. Thermionic Emission: By heating the metal.

2. Photoelectric Emission: By illuminating the metal surface with light (electromagnetic waves like ultraviolet rays) of suitable frequency. The electrons emitted are called photoelectrons.

3. Secondary Emission: Electron emission occurs when a highly energetic electron beam is incident on a metal surface. The emitted electrons are called secondary electrons.

4. Field or Cold Emission: This is the process of electron emission by applying a strong electric field across the metal surface.

Diode Valve

Designed by J. A. Fleming in 1904, the diode valve consists of two electrodes placed inside an evacuated glass envelope. The components of a diode valve are:

• Cathode: Made of tungsten with a thin layer of barium oxide. When heated, the cathode emits electrons.

• Anode (or Plate): The other electrode, which is at a positive potential. The electrons flow from the cathode towards the anode.

As a result, an electric current is established in the circuit. The electrons emitted from the cathode are collected in the space around it. This collection of electrons is called the space charge, which is negative.

A diode valve acts as a rectifier, a device that converts alternating voltage (current) into direct voltage (current).

Triode Valve

Designed by Lee de Forest in 1907, the triode valve is a modified form of the usual diode. It consists of the usual anode-cathode pair and an additional electrode called the control grid.

A triode valve can be used as:

• Amplifier

• Oscillator

• Transmitter

• Detector

Semiconductor

Semiconductors are materials whose electrical conductivity, at room temperature, lies between that of insulators and conductors. Germanium and silicon are two important semiconductors.

In the crystal lattice of a semiconductor, some of the electrons become free from bond formation. At the sites of these free electrons, a deficiency of electrons exists, creating holes that act as virtual positive charges. Semiconductors are widely used in the electronics industry.

Semiconductors are of two types:

1. Intrinsic Semiconductor: A semiconductor in its extremely pure form is known as an intrinsic semiconductor. At absolute zero, an intrinsic semiconductor is a perfect insulator (conductivity = zero).

2. Extrinsic Semiconductor: When a measured and small amount of chemical impurity is added to an intrinsic semiconductor, it becomes an extrinsic semiconductor or doped semiconductor. Doping greatly increases its conductivity.

Extrinsic semiconductors are of two types:

• N-type Semiconductor: An extrinsic semiconductor where electrons are the majority charge carrier. It is made by doping a pure semiconductor with a pentavalent impurity like arsenic, antimony, or phosphorus.

• P-type Semiconductor: An extrinsic semiconductor where holes are the majority charge carrier. It is made by doping a pure semiconductor with a trivalent impurity like gallium, indium, boron, or aluminium.

Additional Information

• Doping: The process of adding chemical impurities to a pure semiconductor to increase its conductivity.

  • Donor: Pentavalent impurities are called donors.

  • Acceptor: Trivalent impurities are called acceptors.

• The electrical conductivity of a semiconductor increases with the increase in temperature.

Rectifier

A rectifier is a device that converts alternating current (AC) into direct current (DC).

Nanotechnology

• The study of science concerning small structures (less than 100 nanometres) is called nanotechnology.

Solar Technology

• Solar cookers and solar PV (photovoltaic) cells both receive energy directly from the sun.

Light Emitting Diodes (LEDs)

• Light Emitting Diodes (LEDs) work on the principle of electroluminescence, which involves the combination of electrons and holes at the junction, releasing energy in the form of light.

Final Thoughts

Electronics is a branch of physics and technology that focuses on the behaviour and movement of electrons. It involves various processes like electron emission, which occurs through methods like thermionic emission, photoelectric emission, secondary emission, and field emission.

Semiconductors, such as silicon and germanium, play a crucial role in modern electronics, with types like intrinsic and extrinsic semiconductors. Rectifiers convert alternating current (AC) into direct current (DC), while components like diode valves and triode valves are used in circuits to control electron flow.

Technologies like nanotechnology and solar energy further illustrate the innovative applications of electronics in everyday life and advanced industries.