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SEMICONDUCTORS

Introduction to Semiconductors

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SEMICONDUCTORS

WE LIVE IN THE AGE OF INFORMATION AS WELL AS THE AGE OF MINIATURIZED ELECTRONICS.

HOW DO WE GET IT?WHERE DOES IT COME FROM?IS IT HELPFUL?ARE OUR LIVES BETTER FOR IT?

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SEMICONDUCTORS

Semiconductors have had a monumental impact on our society.

You find semiconductors at the heart of microprocessor chips as well as transistors.

Anything that's computerized or uses radio waves depends on semiconductors.

We can even grow human tissue on an IC chip

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A semiconductor has an electrical conductivity intermediate in magnitude between that of a conductor and an insulator.

Semiconductors are the foundation of modern electronics, including radio, computers, and telephones.

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Semiconductors are the components that replaced the old style vacuum tubes in electronic equipment

Semiconductors are often referred to as “solid state” components because they are made of solid materials

You can still find vacuum tubes in certain devices…check out an amplifier

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Vacuum tube

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Tiny circuits- there are the equivalent of over 1,000,000 vacuum tubes in these chips

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Semiconductors are the basic building materials used to construct some very important electronic components.

They are used in fire and intrusion alarms.

They are used in microprocessor chips and controllers, cell phones, heaters, pumps, radios, stereos, satellites, anything electrical these days.

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SEMICONDUCTORS

The 3 most commonly used semiconductor devices are:

Diodes

Transistors

Integrated circuits

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Semiconductors are used to control voltage and current to yield a desired result.

An example is using a diode to produce pulsating DC from AC (like a rectifier). A transistor can be used to control resistance to current in a heating element.

An integrated circuit can be used to amplify and modulate a radio signal.

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Advantages of semiconductors:

More rugged than vacuum tubesOperates with very low voltagesCan be “integrated circuits” which replace multiple circuitsSmaller sizeLess weightLess expensive

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Disadvantages of semiconductors

They do not like sudden changes in temperatureThey do not like high heatCan be made to work in these conditions, but need additional componentsMust not subject to voltage extremesNot useful in high power, ultra high radio frequencies

SEMICONDUCTORS

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The semiconductor elements that are suited to the greatest variety of electronic applications are germanium and silicon.

Germanium is a white powder earth element discovered in 1886.

Silicon is a non-metallic element found mainly in the earths crust and was discovered in 1823.

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the element is a gray-white metalloid, and in its pure state is crystalline and brittle, retaining its luster in air at room temperature.

It is a very important semiconductor material. Zone-refining techniques have led to production of crystalline germanium for semiconductor use with an impurity of only one part in 10-10.

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Basic information about and classification of Germanium

• Name: Germanium Symbol: Ge Atomic number: 32

• Atomic weight: 72.64 (1) Period in periodic table: 4

• Colour: greyish white Classification: Semi-metallic

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silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites.

Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen.

It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal. Silicon is found also in minerals such as asbestos, feldspar, clay and mica.

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Basic information about and classifications of silicon:

Name: Silicon Symbol: Si Atomic number: 14

Atomic weight: 28.0855 Period in periodic table: 3

Colour: dark grey/bluish Classification: Semi-metallic

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Semiconductor-based electronic components include transistors, solar cells, many kinds of diodes including the light-emitting diode (LED), the silicon controlled rectifier, photo-diodes, and digital and analog integrated circuits.

In order to understand semiconductors we need to define a few terms first

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An Element is one of the known chemical materials that can not be subdivided into simpler substances

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An Atom is the smallest portion of an element that still exhibits all the characteristics of that element

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Atoms contain three basic components: protons, neutrons and electrons.

The protons and the neutrons are located in the nucleus or center of the atom while the electrons revolve around the nucleus in orbits.

Each element has a specific number of protons in its nucleus and an equal number of electrons in it’s orbit.