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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
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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
Demonstrations Vacuum Tube and CRT Silicon Ingot Individual Transistors Integrated Circuits with lids removed PBS - Transistorized
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
The Diode Reverse Biased:Electrons and holes swept away from the junction, so no current flows in the circuit.
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.
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.
Basic Amplifier Circuit using the NPN Bipolar Transistor http://www.tpub.com
Model of first Transistor c. 1947 http://www.porticus.org/bell
Fabricating a transistor on a single piece of doped silicon wikipedia CNN.com
The Field Effect Transistor (FET) Electricity flows from the Source to the Drain when an electric field is applied to the Gate.
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
Before the transistor, there was the Vacuum Tube • Also used to amplify signals • Also used as a switch
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
Cathode Ray Tube (CRT)Still is use Today Vacuum Tube, Electron Gun, Fluorescent Screen, and Coils which accelerate and deflect the electron beam
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
http://www.porthcurno.org.uk/html/morsecircuit.html 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.
Why was AT&T 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.
ENIAC in 1946 First electronic computer Designed for the Army $500,000 >17,000 Vacuum Tubes 150 KW of power Filled multiple rooms (700 sq. ft) Soldered and constructed by hand by the University of Penn.
Hearing Aids - the first commercial devices that used transistorsc. 1953 http://blog.modernmechanix.com
Some Hearing Aids do not amplify sound:Cochlear Implants bypass portion of the ear that is damaged Cochlear Nerve sends auditory information to the brain. Wikipedia
Cochlear Implant Components • Electrode Array • Receiver • Speech Processor • Transmitting Coil • Microphone http://deafblind.com/cochlear.html
Individual Parts Integration of parts required hand wiring Early Transistor Radio http://vintageradio.me.uk
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
Intel 4004 The World’s 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
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
Sources http://www.pbs.org/transistor/
