Class 10 | Introduction To Electronic Devices | CRM Notes

Matter
Matter is anything that has mass and occupies space. It’s the substance that makes up everything in the universe, from the tiniest subatomic particles to the largest celestial bodies. Matter is typically classified into several categories based on its properties, such as solid, liquid, gas, and plasma. These categories depend on factors like the arrangement of atoms or molecules and the strength of their interactions.

Molecule
A molecule is a group of two or more atoms that are chemically bonded together. These atoms can be of the same element or different elements. When atoms come together to form molecules, they do so through chemical bonds, which involve the sharing or transfer of electrons between atoms. Molecules are the smallest units of compounds that retain the chemical properties of those compounds.
For example: water is a molecule up to two hydrogen atoms and one oxygen atom (H₂O).

Atom
An atom is the basic unit of a chemical element, consisting of a nucleus surrounded by one or more electrons. The nucleus contains protons, which have a positive charge, and usually neutrons, which have no charge. The electrons, which have a negative charge, orbit the nucleus in specific energy levels or shells. Atoms can combine with other atoms through chemical bonds to form molecules and compounds. These bonds are created when atoms share, lose, or gain electrons, resulting in stable arrangements known as molecules or compounds.

Introduction to KCL and KVL

Kirchhoff’s law
Ohm’s law is used to analyse current, voltage, and resistance in simple circuit but kirchhoff’s  law can be used to calculate values in complex circuits.

1. Kirchhoff’s current law
   this law is also known as kirchhoff’s first law or kirchhoff’s junction law. According to the statement, “in a closed network of conductor, the algebraic sum of current meeting at a node is point.” Alternating, current flowing towards a junction in a closed network system is equal to current flowing away from the same junction. Current exiting a junction will have a negative sign if the current entering the junction has positive sign.

For the figure shown above, applying KCL at node, we get,

I₁+ I₂+ I₃= I₄+ I₅

Or, I₁+ I₂+ I₃-I₄ –I₅=0
this can be generalised to the case with n wire all connected at a node by writing:

1. Kirchhoff’s voltage law
   This law is also known as kirchhoff’s second law or kirchhoff’s loop law. It states that, in a closed loop, the algebraic sum of all the potential differences is zero.” Alternating, in any closed loop, the algebraic sum of all electromotive force of sources and potential drops in the load is equal to zero. While one moves from lower potential to higher potential, there is gain in potential difference in direction of movement is taken as positive and while moving from higher to lower potential, there is fall in potential so this potential difference in the direction of movement is taken as negative.

   for the figure shown above, applying KVL in loop, we get,
   R₁+R₂+R₃+R₄+R₅=V_S
   or, R₁+R₂+R₃+R₄+R₄-V_S

KVL can be generalised to any loop containing any number of components. A more formal way of writing it is

Introduction to semiconductor material

Semiconductors are substance with conductivity that is the intermediate of that of metals and insulators. The most common semiconductor material is silicon, but other materials such as germanium, gallium arsenide, and other are also used in wide range of electronic devices, solar cells, LED lights, and sensors also. There are two types of semiconductor. They are:

1. 
   A) Intrinsic semiconductor
   an intrinsic semiconductor is a pure semiconductor, which means it does not have any impurities added to it. In an intrinsic semiconductor, the number of free electrons and holes in equal. Silicon and germanium are examples of intrinsic semiconductors.

 

1. B) Extrinsic semiconductor
   an extrinsic semiconductor is a semiconductor that has been intentionally doped with impurities to alter its electrical properties.

 

Doping

The conductivity of metal is increased by adding an appropriate amount of suitable impurities. This process is known as doping. Based on type of impurities added, extrinsic  semiconductor are classified into two types. They are:

N-type semiconductor:
An N-type semiconductor is doped with impurities that have more electrons than the intrinsic semi-conductor. It is referred to as an N-type semiconductor when a pentavalent impurity atom is added to an inherent semi-conducting atom, such as silicon or germanium. 

P-type semiconductor:
A P-type semiconductor is doped with impurities that have fewer electrons the intrinsic semi-conductors. It is referred to as a P-type semiconductor when a trivalent impurity atom is added to an inherent semi conducting atom, such as silicon and germanium.

 

Majority and Minority charge carrier

 Majority charge carrier
they are the most abundant type of charge carries in a semiconductor. They are created by doping the semiconductor with impurities that either introduce excess electrons or create vacancies for electrons. Majority carries p type semiconductors are holes.

Minority charge carrier
minority carries, on the other hand, are present in smaller quantities than the majority carries. They are created by thermal excitation or by the action of external sources such as light. Minority carries in n type semiconductor is a free electrons.

 

PN Junction formation

PN junction is a type of semiconductor which is formed by bringing together a P-type and N-type semiconductor. To form the PN junction we take p type semiconductor having Majority carries holes and minority carries electrons and one n type semiconductor with majority carries as free electrons and minority carries as holes. And we join p and n type semiconductor with help of special fabrication technique. When we join these two material a junction formed know a PN junction.

 

Forward Biased

When p type region of PN junction we connected to positive terminal and n type region is connected to the negative terminal of battery, then it is said to be forward bias.

Reverse Biased
If external voltage is applied with positive terminal to n side and negative terminal to P side, then the junction is said to be a reverse bias.