Fundamentals of Electronics - Semi Conductors | Conducts | Insulators

Classification of Materials:

Conductor: It is a material which conducts electricity, the conductivity of conductor is very high and resistance is so low.
In conductor electrons are charge carriers, the resistance of conductor increases with increase in temp. Impurity decreases the conductivity of conductor, in energy band diagram of conductor the conduction band and valence band overlap each other so that the charge flow is easy and fast.

 Example of conductors are: Copper (cu), Aluminum (Al), Silver (Ag), etc.
 Application of conductors : In production of electric wires.


Insulator: A material which doesn't conduct electricity is called an insulator. The conductivity of insulator is very low and the resistance is so high.
There is no charge carrier and no effect of temperature because its resistance coefficient is zero.
(NOTE: Resistance coefficient: The resistance-change factor per degree Celsius of temperature change is called the temperature coefficient of resistance.)
There is no change by adding any impurity in insulator.
In insulator, the forbidden energy gap between conduction band and valance band is very high. 
Example: Rubber, plastic, etc.
Application: Insulating layers of wires or coating.

But before knowing semi-conductor, you might be thinking what the hell is Covalent and Valence bond.. right? So let's go through the definitions of Covalent and valance bons.
In an energy band diagram, there are three things namely, defined below.

1. Valence bond:  The range of energy possessed by valanced electrons is called valence band. Electrons in the outermost orbit of the atom are called valance electrons, in a normal atom valence band has the electron of highest energy.

2. Conduction band: The valence electrons are losely attatched to the nucleaus at ordinary temprature, some of the valence electrons get detached to become free, in this band the electrons can gain energy from external electric field these free electrons are responsible for flow of current so they are called conduction electrons and the range of energy possessed by conduction electron is known as conduction band.

3.Forbidden energy gap(Fermi level gap):  In between the lowest level of conduction band and highest level of valence band there is a gap that can't be occupy by the electrons which is called forbidden energy gap or band gap. In order to pose an electron from valence band to the conduction band, external energy equal to the forbidden energy gap must be supplied. In the image below the forbidden energy gap is represented by "Band Gap".

Semi-Conductor: It is a material whose property lies between insulator and conductor (conductivity and resistance).

*In semi conductor the electrons and holes are charge carriers (Electrons for -ve and holes for +ve)

*The resistance of semi conductor decreases with rise in temperature.

*Impurity increases the electric conductivity of semi conductor.

*Conduction band and valence band are separated by very small forbidden energy gap of about 1 eV (electro-volt).

Example: Silicon and germanium.

Application: Semiconductor devices, etc.

As we're focusing on the topic "Semi-conductor"so let's go in detail about them.

Types of Semiconductor: 

1. Intrinsic Semiconductor (Pure Semiconductor): In these types of semi conductors the electrical conductivity is totally governed by no. of electrons excited from valence band to conduction band.

example of intrinsic semiconductors are silicon and germaniam.

Both silicon and Ge have four electrons in the outermost shell which are called valence electrons. The four valence electrons form four covalent bonds with adjacent Si or Ge atom.

At absolute 0 temperature all the valence electrons are tightly bound to each Si atom there is no free electron is available for conduction so an intrisic semi conductor (Semi-C) behaves as insulator at absolute 0 temp. but at room temp. (25 - 27 degree celcius) or (300 kelvin)  the energy of electron become so sufficient and covalent bonds get broken and the electrons become free they now move to the conduction band.

*The place where electrons are not present is called hole. the hole is considered as an active particle of valence band.

*In an intrinsic semi-C the total no. of electrons are equal to the total no. of holes.

*Below, the image shows electric conduction in intrinsic semiconductor:

2. Extrinsic Semiconductor: When a small quantity of pentavalent or trivalent impurity is introduced into pure semi conductor (intrinsic semi-c) its electrical conductivity increases and they become extrinsic semiconductors or impure semiconductors. 

Doping: It is the process of adding impurity to an intrinsic semiconductor.

According to impurity added in pure semi-c it gets divided into two categories.

(i) N-type semi conductor: When a small quantity of pentavalent impurity such as antimony or arscenic is added to a pure semi conductor than the large no. of free electron are generated and this type of semi-conductor becomes N-type semi-c. 

(ii) P-Type Semi-conductor: When a small quantity of trivalent impurity like boron or indium is added to pure semi conductor then the large no. of holes are generated, such type of semi-c is called p-type semi-c. In P-type semi conductor Holes are major charge carriers and Electrons are minor charge carriers.

Note: Don't get confused in types of impurity, remember it with this trick- "P for N & T for P" (Pentavelant for N-type & Trivalent for P-type).

Data Structures - Introduction

Data may be single valued or may be multiple values, the data to be proceed must be organized in a particular structure. Which is structuring of data and hence the data structures are studied.
Now, what is a data structure? Exactly? Well as you know the data may be organized in many different forms such as linear form, tree form and stuff that we'll discuss later on.
Alternatively, The logical or mathematical model of a particular organization of data is known as a data structure.
There are mainly two types of data structure - Linear data structure and Non-linear data structure.
Linear data structure: In this type of data structure, the processing of data is done in linear way, which means the data can be proceed by the compiler in a sequential manner.
Linear data structures are : 1. Array
Arrays are most frequently used in programming. Mathematical problems like matrix, algebra and etc can be easily handled by arrays. An array is a collection of homogeneous data elements described by a single name. Each element of an array is referenced by a sub-scripted variable or value, called subscript or index enclosed in parenthesis. If an element of an array is referenced by single subscript, then the array is known as one dimensional array or linear array and if two subscripts are required to reference an element, the array is known as two dimensional array and so on. Analogously the arrays whose elements are referenced by two or more subscripts are called multi dimensional arrays.
Example of one dimensional array and multidimensional array:
                                                                                                              
                                                                                                        
2. Stack:
A stack is one of the most important and useful non-primitive linear data structure in computer science. It is an ordered collection of items into which new data items may be added/inserted and from which items may be deleted at only one end, called the top of the stack. As all the addition and deletion in a stack is done from the top of the stack, the last added element will be first removed from the stack. That is why the stack is also called Last-in-First-out (LIFO) .Note that the most frequently accessible element in the stack is the top most elements, whereas the least accessible element is the bottom of the stack. The operation of the stack can be illustrated as in figure below:
                                                                                                      
The insertion (or addition) operation is referred to as push, and the deletion (or remove) operation as pop. A stack is said to be empty or underflow, if the stack contains no elements. At this point the top of the stack is present at the bottom of the stack. And it is overflow when the stack becomes full, i.e., no other elements can be pushed onto the stack. At this point the top pointer is at the highest location of the stack.
3. Queues:
A queue is logically a first in first out (FIFO or first come first serve) linear data structure. The concept of queue can be understood by our real life problems. For example a customer come and join in a queue to take the train ticket at the end (rear) and the ticket is issued from the front end of queue. That is, the customer who arrived first will receive the ticket first. It means the customers are serviced in the order in which they arrive at the service centre. It is a homogeneous collection of elements in which new elements are added at one end called rear, and the existing elements are deleted from other end called front. The basic operations that can be performed on queue are 1. Insert (or add) an element to the queue (push)
                                                    2. Delete (or remove) an element from a queue (pop)
                                                                                                            

Non-linear data structure: The data structures in which insertion, deletion and processing of data can not be done in linear way are called non-linear data structures.
types of non-linear data structure:
1. Trees:
A tree is an ideal data structure for representing hierarchical data. A tree can be theoretically defined as a finite set of one or more data items (or nodes) such that : 1. There is a special node called the root of the tree. 2. Removing nodes (or data item) are partitioned into number of mutually exclusive (i.e., dis-joined) subsets each of which is itself a tree, are called sub tree.
                                                                                                                            
2. Graphs: Graphs representations have found application in almost all subjects like geography, engineering and solving games and puzzles. A graph G consist of 1. Set of vertices V (called nodes), (V = {v1, v2, v3, v4......}) and 2. Set of edges E (i.e., E {e1, e2, e3......cm} A graph can be represents as G = (V, E), where V is a finite and non empty set at vertices and E is a set of pairs of vertices called edges. Each edge ‘e’ in E is identified with a unique pair (a, b) of nodes in V, denoted by e = [a, b].