PPT Based on Analog electronics -I Introduction to Electronic materials include: Conductors: have low resistance which allows electrical current flow Insulators: have high resistance which suppresses electrical current flow Semiconductors: can allow or suppress electrical current flow

Conductor Good conductors have low resistance so electrons flow through them with ease. Best element conductors include: Copper, silver, gold, aluminum, & nickel Alloys are also good conductors: Brass & steel Good conductors can also be liquid: Salt water

The atomic structure of good conductors usually includes only one electron in their outer shell. It is called a valence electron. It is easily striped from the atom, producing current flow. Copper Atom A presentation of eSyst.org

Insulators Insulators have a high resistance so current does not flow in them. Good insulators include: Glass, ceramic, plastics, & wood Most insulators are compounds of several elements. The atoms are tightly bound to one another so electrons are difficult to strip away for current flow. A presentation of eSyst.org

Overview Introduction What are P-type and N-type semiconductors?? What are Diodes? Forward Bias & Reverse Bias Characteristics Of Ideal Diode I – V Characteristics of Diodes Rectifiers

Introduction Semiconductors are materials whose electrical properties lie between Conductors and Insulators. Ex : Silicon and Germanium

What are P-type and N-type ? Semiconductors are classified in to P-type and N-type semiconductor P-type: A P-type material is one in which holes are majority carriers i.e. they are positively charged materials (++++) N-type: A N-type material is one in which electrons are majority charge carriers i.e. they are negatively charged materials (-----)

Diodes Electronic devices created by bringing together a p-type and n-type region within the same semiconductor lattice. Used for rectifiers, LED etc

Diodes It is represented by the following symbol, where the arrow indicates the direction of positive current flow.

Forward Bias and Reverse Bias Forward Bias : Connect positive of the Diode to positive of supply…negative of Diode to negative of supply Reverse Bias: Connect positive of the Diode to negative of supply…negative of diode to positive of supply.

Characteristics of Diode Diode always conducts in one direction. Diodes always conduct current when “Forward Biased” ( Zero resistance) Diodes do not conduct when Reverse Biased (Infinite resistance)

I-V characteristics of Ideal diode

I-V Characteristics of Practical Diode

Rectifiers and its type: Rectifiers :  rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which is in only one direction, a process known as rectification.

Types of Rectifiers Half wave rectifier Full wave rectifier Center tape full wave rectifier Bridge rectifier

Half wave rectification

Working Of Half wave Rectifier In Half Wave Rectifier one step down transformer & one diode are used. So it convert half wave of a.c into d.c

Full wave rectification For single-phase AC, if the transformer is center-tapped, then two diodes back-to-back (i.e. anodes-to-anode or cathode-to-cathode) can form a full-wave rectifier.

Full wave rectifier using transformer and 2 diodes

Full wave rectifier using transformer and 2 diodes In a circuit with a non - center tapped transformer, four diodes are required instead of the one needed for half-wave rectification.

Full wave rectifier working animation

Working A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-wave rectification. It convert both half cycle of a.c into d.c.its efficiency higher then center tape full wave rectifier .

Transistors What is a Transistor? History Types Characteristics Applications

What is a Transistor? Semiconductors: ability to change from conductor to insulator Can either allow current or prohibit current to flow Useful as a switch, but also as an amplifier Essential part of many technological advances

A Brief History Guglielmo Marconi invents radio in 1895 Problem: For long distance travel, signal must be amplified Lee De Forest improves on Fleming’s original vacuum tube to amplify signals Made use of third electrode Too bulky for most applications

The Transistor is Born Bell Labs (1947): Bardeen, Brattain, and Shockley Originally made of germanium Current transistors made of doped silicon

How Transistors Work Doping: adding small amounts of other elements to create additional protons or electrons P-Type: dopants lack a fourth valence electron (Boron, Aluminum) N-Type: dopants have an additional (5th) valence electron (Phosphorus, Arsenic) Importance: Current only flows from P to N

Bipolar Junction Transistor (BJT) 3 adjacent regions of doped Si (each connected to a lead): Base. (thin layer,less doped). Collector. Emitter. 2 types of BJT: npn. pnp. Most common: npn (focus on it). npn bipolar junction transistor pnp bipolar junction transistor