Transistors

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Transistors
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Definition

• An electronic device made of a semiconductor that
  can act as an insulator and a conductor.
• The ability to change from these two states
  enables the device switch or amplify.
• It has of three components
• Source
• Gate
• Drain

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Transistors
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Transistors

• Transistors replaced vacuum tubes.
• Transistors are central to the Integrated
  Circuit, and
• therefore, all electronic devices of the
  information age, such as
• pcs, cellular phones, ipods, pdas, intelligent
  cars and buildings.. are made possible.

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How a Transistor Works

• The transistor can function as
• An insulator
• A conductor
• The transistor's ability to fluctuate between
  these two states that enables to switch or
  amplify.

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How a Transistor Works

• The transistor has many applications, but only
  two basic functions
• switching and modulation (amplification).
• In the simplest sense, the transistor works like
  a dimmer.

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How a Transistor Works

• With a push the knob of the dimmer, the light
  comes on and off.
• You have a switch.
• Rotate the knob back and forth, and the light
  grows brighter, dimmer, brighter, dimmer.
• Then you have a modulator.

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the dimmer
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How a Transistor Works cont.

• Both the dimmer and the transistor can control
  current flow.
• Both can act as a switch and as a
  modulator/amplifier.
• The important difference is that the hand
  operating the transistor is millions of times
  faster.

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How a Transistor Works cont.

• Transistors are made of semi-conductors such as
  silicon and gallium arsenide.
• These materials carry electricity not well enough
  to be called conductors
• not badly enough to be called insulators.

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How a Transistor Works cont.

• Hence their name semiconductor.
• The importance of a transistor is in its ability
  to control its own semi conductance,
• namely acting like a conductor when needed, or as
  an insulator (nonconductor) when that is needed.

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How a Transistor Works cont.

• You can compare a transistor to an ordinary
  faucet.
• The water enters the faucet in the pipeline from
  the water distributor, which would correspond to
  the source in the Transistor.
• The water then leaves the faucet into the sink,
  this would be the drain in the Transistor.

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How a Transistor Works cont.

• The water tap controls the amount, flow, of
  water.
• In the Transistor the gate operates as this
  controller.
• With a small force you can control the water flow
  with the water tap, just as you can control the
  current flowing from the source to the drain,
  with a small change of the charge of the gate.

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Transistors are Made of Silicon

• Silicon is a grey colored element with
  crystalline structure.
• It is the second most abundant element in the
  earth's crust, after oxygen.
• Silicon is always found in combined form in
  nature, often with oxygen as quartz, and is found
  in rocks and silica sand.

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Transistors are Made of Silicon

• To be able to use silicon as a semiconductor, it
  needs to be in a very pure form.
• If there is more than one impure particle in a
  million, the silicon can not be used.
• Silicon is the most frequently used
  semiconducting material today.

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Doping

• The addition of a small amount of a different
  substance to a pure semiconductor crystal.
• The impurities give an excess of conducting
  electrons or an excess of conducting holes which
  is crucial for making a working transistor.

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n-type doping
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p-type doping
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Conduction Band
Is a part in which electrons can move freely and
can accelerate under an electric field,
constituting an electric current.
Energy Gap Is the energy difference between the
valence gap and the conduction band
Valence Band Is a part of the molecule, called
band, where you can find the electrons
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Transistor types

• MOS - Metal Oxide Semiconductor
• FET - Field Effect Transistor
• BJT - Bipolar Junction Transistor

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Moores Law

• Its an observation made by Gordon E. Moore, in
  which he predicted that the number of
  transistors, inside an Integrated Circuit, could
  be doubled every 24 months.
• At the density that also minimized the cost of a
  transistor.

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http//upload.wikimedia.org/wikipedia/commons/0/06
/Moore_Law_diagram_28200429.png
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Pictorial History of Transistors
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http//www.bellsystemmemorial.com/belllabs_transis
tor.html