Introduction to Electronics by V K Mehta

Study Notes

Introduction to Electronics

Electronics is the branch of physics and engineering concerned with the design of circuits using transistors and microchips, and with the behavior and movement of electrons in a semiconductor, conductor, vacuum, or gas.
Electronics is also the science of how to control electric energy.
Basic electronic components include resistors, capacitors, inductors, transformers, diodes, transistors, and integrated circuits.

Resistance

The resistance of a material is the opposing force that a flowing charge encounters.
All materials have a resistance that is dependent on cross-sectional area, material type, and temperature.
A resistor dissipates power in the form of heat.
A resistor in an electronic circuit can be in series, parallel, star, or delta.

Capacitor

A capacitor is used to store charge for a short amount of time.
A capacitor is a device that stores energy in an electric field, consisting of two conductive plates separated by a non-conductive material.
Capacitors are rated by the amount of charge that can be held (in Farad) and the voltage handling capabilities.

Semiconductors

Semiconductors are classified into two types: intrinsic and extrinsic.
Intrinsic semiconductors contain no impurities and no crystalline defects.
Extrinsic semiconductors are classified into two types: N-type and P-type.

N-type Semiconductors

N-type semiconductors contain more electrons than holes.
In an N-type semiconductor, conduction is mainly due to electrons (negative charges).
Positive charges (holes) are the minority carriers.

P-type Semiconductors

P-type semiconductors contain more holes than electrons.
In a P-type semiconductor, conduction is mainly due to holes (positive charges).
Negative charges (electrons) are the minority carriers.

Carrier Movement

There are two mechanisms by which holes and free electrons move through a silicon crystal: drift and diffusion.
Drift current is generated by the electrical field across a piece of silicon.
Diffusion current is generated by the different concentration of carriers in a piece of silicon.

Silicon

Silicon is a tetravalent element, which means it has four valence electrons and four vacancies.
In intrinsic (pure) silicon, atoms join together by forming covalent bonds.
Each atom shares its valence electrons with each of four adjacent neighbors, effectively filling its outer shell.

Electronic Properties of Si

Silicon is a semiconductor material.
Pure Si has a relatively high electrical resistivity at room temperature.
There are two types of mobile charge-carriers in Si: electrons (negatively charged) and holes (positively charged).

Intrinsic Semiconductors

A semiconductor is said to be intrinsic if it contains no impurities and no crystalline defects.
The structure has zero overall charge.
At absolute zero, every electron is at the lowest energy state, and the states in the conduction band are empty.
Electrons leaving the VB to CB creates a vacancy called hole in the valence band.

Thermal Generation and Recombination

At room or higher temperatures, electrons acquire thermal energy, which is transferred to them from the crystal lattice.
Phonons can excite electrons from the valence band (VB) to the conduction band (CB).
Electrons leaving the VB to CB creates a vacancy called hole in the valence band.
The free electrons in the semiconductor can fall into holes in a process known as recombination.
Energy is given up by the electrons in this process.

Description

This quiz covers the basics of electronics, including the definition and concepts of electronics, with reference to V K Mehta's book. Topics include the design of circuits using transistors and microchips, and the behavior of electrons in various materials.