Diodes

What is a diode?

A diode is the simplest form of semi conductor device

What is a semi conductor?

A semi conductor is defined as a solid whose electrical conductivity can be controlled. solidelectrical conductivity solidelectrical conductivity

The Solid that is used in most semi conductors is Silicon which is not to be mistaken with silicone which is used for many thing such as caulking around doors

SiliconSilicon is the most commercially important semiconductor used today. Silicon

Raw Silicon is a excellent insulator which would mean that is a terrible choice for moving electrons.

The atomic stucture of Raw Silicon is transformed by a process called Doping.

Doping is the process of introducing small amounts of another compond to change the atomic structure of Silicon

Two of the most common compounds are Boron and Phosphorus Boron PhosphorusBoron Phosphorus

Phosphorus is introduced to raw Silicon to create a compound that has an excess of electrons which makes it a good conductor of electricity with negative properties. It is classified as a N-type semiconductor. Phosphorus

It is said that the electrons in N-type Silicon are the Majority Carriers and the holes are the Minority Carriers

What are holes In an abstract way holes are the space left when an electron moves. A good way of understanding this is to think of removing an egg from an egg tray. When you remove the egg a hole is left behind. In an abstract way holes are the space left when an electron moves. A good way of understanding this is to think of removing an egg from an egg tray. When you remove the egg a hole is left behind.

BoronBoron is introduced to raw Silicon to create a compound that has an excess of holes. This makes it a good conductor of electricity with positive properties. It is classified as a P-type semiconductor. Boron

It is said that in P-type Silicon the holes are the Majority Carriers and the electrons are the Minority Carriers

Materials with more of one type of charge carrier than the other are called extrinsic. The charge carrier present in greater numbers is called the Majority Carrier. Materials with exactly the same number of both types of carriers are called intrinsic. Materials with more of one type of charge carrier than the other are called extrinsic. The charge carrier present in greater numbers is called the Majority Carrier. Materials with exactly the same number of both types of carriers are called intrinsic.

In the simpliest terms a diode is a device that is comprised of two pieces of semi conductor material that are joined together. One piece of silicon would be N-type silicon and the other would be P- type silicon

The main purpose of a diode is to allow electrons to flow in one direction without resistance and restrict electrons from flowing in the other direction.

This is the schematic symbol for a diode

For electricity to flow through a diode it must be forward biased.

A forward biased diode will have the Anode connected to the more positive side of the circuit and the Cathode connected to the more negative side of the circuit

For a diode to work in a forward biased configuration it must be turned on. To turn on a diode requires about.7 Volts to drop over the diode.

If a diode is placed in the circuit the other way it is said to be reverse biased. In this configuration electricity will not flow

Forward bias - all current, almost no volts. Reverse bias - all volts, almost no current.

Diodes are used for many reasons. One very important reason is to stop current flowing the wrong way through a circuit which can happen by placing a battery in backwards.

Another is to convert AC Voltage to DC Voltage

The picture below shows the association between the schematic picture of a diode and the colour coding of a diode Notice that the white band on the diode is at the Cathode end of the diode