Table of Contents
- Electronic Devices
- Types of electronic devices
- Some of the important features of the semiconductor devices are as follows:
- Some important points regarding electronic devices
Electronic Devices
The discovery of the electron was a landmark in physics and has led to a great technological advance. The present-day instant communication with the entire world is the result of the multifarious uses of these electrons.
As an electron is a light particle having a negative charge, so it can be easily manipulated with the expenditure of a small amount of energy i.e., it can be made to attain high speeds and its direction can be easily changed, as desired, by means of suitable electric and magnetic fields. In fact, an electron can be made to attain speeds nearing an appreciable fraction of the speed of light in free space. This high speed makes its instant action possible.
Any device whose action is based on the controlled flow of electrons through it is called an electronic device. The branch of physics that deals with the study of these electronic devices is called electronics. Electronic devices are the basic building blocks of all the electronic circuits.
Types of electronic devices
The electronic devices are of two basic types:
A. Vacuum tubes:
These include vacuum diodes (consisting of two electrodes – cathode and anode), triode (with three electrodes) and pentode (with 5 electrodes).
Some of the important features of vacuum tubes are as follows:
- In vacuum tubes, electrons are obtained from a heated cathode and the flow of electrons is controlled by varying the voltage between its different electrodes.
- A vacuum is necessary in the interelectrode region so that the electrons may not lose their energy on colliding with air molecules in their path.
- As the electrons can flow only in one direction i.e., from cathode to anode, so vacuum tubes are also known as vacuum valves.
- The vacuum tubes are bulky, consume high power and operate generally at high voltages (~ 100 V).
- They have limited life and low reliability.
B. Solid-state electronic devices:
In 1930’s, it was first realised that some solid-state semiconductors and their junctions offer the possibility of controlling the number and direction of flow of charge carriers through them. Semiconductors are the basic materials used in the present solid electronic devices like junction diode (a 2-electrode device), transistor (a 3-electrode device) and integrated circuits (ICs).
Some of the important features of the semiconductor devices are as follows:
1. In a semiconductor device, simple excitations like light, heat or small applied voltage can change the number of charge carriers.
2. The charge carriers flow in the solid itself, no vacuum has to be created for the flow of charges as required in vacuum tubes.
3. It does not require any cathode heating for the production of charge carriers. So it starts operating as soon as it is switched on.
4. Semiconductor devices are small in size, consume low power and operate at low voltages.
5. They have long life and high reliability.
Some important points regarding electronic devices
- Much before the discovery of semiconductor devices, a naturally occurring crystal galena (Lead sulphide: PbS) with a metal point contact attached to it was used as detector of radio waves.
- The use of semiconductors to develop junction diodes and transistors has great advancement in electronics. The miniaturisation of various electronic gadgets became possible with’ the use of semiconductor devices and a continuation of this process led to the discovery of integrated circuits.