The Transistor

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The Transistor

• How does a Transistor work
• The Bipolar Transistor
• The Field Effect Transistor
• Comparing a Transistor to other devices
• Diode vs. the Transistor
• Vacuum Tubes and Relays vs. the Transistor
• Benefits of using transistors
• Able to amplify an alternating signal
• Used as a fast switch
• Low Power
• Solid state and small in size
• Inexpensive
• First uses of Transitors
• Replaced Vacuum tubes in radios and computers
• Hearing Aids
• Airplanes
• 4004 First single chip Microprocessor where
  transistors are integrated on a single piece of
  Silicon

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Demonstrations

• Vacuum Tube and CRT
• Silicon Ingot
• Individual Transistors
• Integrated Circuits with lids removed
• PBS - Transistorized

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What is a Transistor

• Made of doped semiconductor materials, the
  transistor is used to amplify electrical signals
  or used as a switch.

http//fourier.eng.hmc.edu
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The Diode Forward Biased Current flows
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The Diode Reverse BiasedElectrons and holes
swept away from the junction, so no current flows
in the circuit.
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The Bipolar NPN Transistor
The base-emitter junction is forward biased, the
base-collector junction is reverse biased. The
transistor is bipolar because both charge
carriers (holes and electrons) are present.
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• By doping (adding impurities to) a semiconductor
  material (i.e. Silicon or Germanium), very
  different electrical properties are created.
• By sandwiching these dissimilar materials, a
  transistor is made.
• If the base is thin, electrons from the emitter
  are swept though the base to the collector.
  Electrons in the collector then respond to the
  positive voltage and flow out of the collector.

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Basic Amplifier Circuit using the NPN Bipolar
Transistor
http//www.tpub.com
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Model of first Transistor c. 1947
http//www.porticus.org/bell
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Fabricating a transistor on a single piece of
doped silicon
wikipedia
CNN.com
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The Field Effect Transistor (FET)

• Electricity flows from the Source to the Drain
  when an electric field is applied to the Gate.

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Field Effect Transistor (FET)

• FETs are tiny switches that can open and close
  very quickly.
• A negative voltage will turn this p-channel
  transistor on. On means there is a connection
  between the Source and Drain.

http//www.answers.com
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Before the transistor, there was the Vacuum Tube

• Also used to amplify signals
• Also used as a switch

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A grid controls the electron flow. The signal to
be amplified is connected to the grid. A small
signal controls a much larger voltage
Electrons are boiled off the cathode
and attracted to the anode because of the applied
voltage.
http//www.privateline.com
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Cathode Ray Tube (CRT)Still is use Today

• Vacuum Tube, Electron Gun, Fluorescent Screen,
  and Coils which accelerate and deflect the
  electron beam

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Prior to Vacuum tube

• No coast-to-coast telephone calls
• Wireless Telegraph in use Morse codes received
  and boosted using relays.
• Alternating Signals could not be amplified with
  relays
• Signals were sent over wires no farther than NY
  to Denver

Relay switch that opens and closes and
is controlled by current in another circuit. Two
settings OPEN And CLOSED
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http//www.porthcurno.org.uk/html/morsecircuit.htm
l
On or Off, current is either constant or it does
not flow.
Applying a small varying signal (voice signal)
here would not produce a varying signal in the
top circuit.
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Why was ATT interested in the Transistor?

• Vacuum Tubes were unreliable for amplifying
  signals in transcontinental telephone calls.
• Vacuum Tubes consumed a lot of power and got hot.
• Competition from other phone companies made
  reliable and fast phone service important.

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ENIAC in 1946

• First electronic computer
• Designed for the Army
• 500,000
• gt17,000 Vacuum Tubes
• 150 KW of power
• Filled multiple rooms (700 sq. ft)
• Soldered and constructed by hand by the
  University of Penn.

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Hearing Aids - the first commercial devices that
used transistorsc. 1953
http//blog.modernmechanix.com
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Some Hearing Aids do not amplify soundCochlear
Implants bypass portion of the ear that is damaged
Cochlear Nerve sends auditory information to the
brain.
Wikipedia
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Cochlear Implant Components

1. Electrode Array
2. Receiver
3. Speech Processor
4. Transmitting Coil
5. Microphone

http//deafblind.com/cochlear.html
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http//transistorhistory.50webs.com/maico.html
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• Individual Parts
• Integration of parts required hand wiring

Early Transistor Radio http//vintageradio.me.uk
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The birth of the integrated circuit (IC)

• 1947- using silicon as a transistor is discovered
• 1959- Texas Instruments put 10 transistors on one
  piece of silicon. First company to use Silicon
  instead of Germanium
• Used in Apollo Program to achieve moon landing
  transistors integrated on pieces of silicon
  offered lower power and weight. 1961-69

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Intel 4004 The Worlds first Microprocessor, made
in 1971 Computer on a chip! It had 2300
transistors and ran at 740 KHz. It could execute
45 instructions. Could execute 96,000
instructions per second As powerful as the ENIAC
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Wheres the chip?
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http//www.computerhistory.org/semiconductor/
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Chips can have millions of transistors built on a
small piece of silicon.
CMOS stands for Complimentary Metal Oxide
Semiconductor. This means CMOS chips contain
both pMOS and nMOS transistors.
http//www.britannica.com
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Sources

• http//www.pbs.org/transistor/