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12.02.10 1
05-Semiconductors and Display Devices
Semiconductor Materials Diodes Transistors Monolithic Microwave integrated Circuits(MMIC) Light-Emitting Diodes(LEDs) Liquid-Crystal Displays(LCDs) Cathode Ray Tubes(CRTs) Vidicons Charge-Couped Devices(CCDs)
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Semiconductors
Silicon Si NOT Silicone Germanium Ge Gallium Arsenide GaAs Gallium Nitride GaN Others
Lead sulfide PbS aka Galena Copper Oxides CuOx Selenium Se
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N-Type and P-Type
Semiconductors Intrinsic or pure, crystal
4 of 8 Valence Electrons N-type
Majority Carriers are Free-Electrons Donor Impurities, 5 Valence Electrons
Arsenic As and Antimony Sb
P-type Majority Carriers are Holes Acceptor Impurities, 3 Valence Electrons
Gallium Ga and Indium In
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The PN Junction without bias
Free-electrons (Black Dots) Majority Carries in N-type Cross over to the P-type fill in the Holes
Holes (Red Dots) Majority Carrier in P-type Filled by Free Electrons Forming a depleation-zone
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Reversed-Bias PN Junction
The Negitive chargeThe Majority Carriers are pulled from the junction
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Forward-biased PN Junction
The Free-Electrons and Holes are at the junction
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Diodes
Junction Diodes Point Contact Diodes Hot-Carrier Diodes Schotty Barrier Diodes Zener Diodes Tunnel Diodes Varactor Diodes PIN Diodes
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Junction Diodes
Used for Rectifiers Diode Ratings
Maximum Average Forward Current Determined be Junction Temperature
Peak Inverse Voltage(PIV)
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Point Contact Diode
First Diode http://bizarrelabs.com/foxhole.htm Cat-Whisker or just Whisker of Aluminum
Forms a metal-semiconductor Junction Low-Capacitance Used for UHF Mixers and VHF detectors
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Hot-Carrier Diode
Metal-Semiconductor Junction Like point-contact(below-left) But the contact is a metel dot(below-right) http://www.radio-electronics.com/info/data/semicond/schottky_diode/schottky_barrier_diode.php
Superior to Point-contact mechanically and electrically
Used for VHF/UHF mixers and detectors
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Schottky Diode
Both Point-Contact and Hot-Carrier Diodes are examples of Schottky Diodes The forward voltage drop is around .2 to .5 Volts Limited PIV Reverse-bias leakage current
In the schematic symbol for the Schottky Diode the cathode looks like a ”S”
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Zener Diode
Reversed-bias Extra dopents make the diode conduct with a
steady reverse-voltage drop Large increase in current while litter change in
voltage
A current-limiting resistor keeps the reverse-current to a safe, approx 80% level.
Symbol for the cathode looks like a ”Z”
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Tunnel Diode
Negitve-resistance region Voltage increase as current decrease
Used in amplifiers and oscillators Symbol look like a the arrow is going under in a
tunnel
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Varactor Diode
Reversed-biased to form a capacitor Depleation Zone widens to decrease capacitance Known as a capacitance diode Varicap is a trade name Symbol show a form of a capacitor
The one on the right is what is on the test
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PIN Diode
P-Intrinic-N
Used in RF Switches and Attenuators
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Transitors
Bipolar Junction Transistor(BJT) Uni-Junction Transistor(UJT) Junction Field-Effect Transistor(JFET) Metel-Oxide Semiconductor FET(MOSFET)
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Junctions in BJT
Bipolor Junction Transistors Emitter heavy-doped Base lightly-doped AND Thin Collector lightly-doped
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Biasing a BJT
Emitter-Base Junction is forward-biased Base-Collector Junction is reversed-biased An example with NPN
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Junction Field Effect Transistor
The three terminals of a JFET are Source(compared to a BJT's emitter) Gate(compared to a BJT's base) Drain(compared to a BJT's collector) Symbol to right in for a P-channel JFET
The JFET has a Zin of about 1 MΩ Transconductance(compared to BJT's beta)
Measured in Siemens(S) gm=I dV gs
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MOSFET
Gate diode protects Gate insulation from static Arrow points iN for a N-channel Symbol to Below is for a Dual-Gate N-Channel
MOSFET Depletion Mode Enhancement Mode Depletion-Enhancement Mode The make of MOSFETs http://www.ece.byu.edu/cleanroom/virtual_cleanroom.parts/MOSFETProcess.html
V gs0 I d0
V gs=0 I d=0
V gs=0 I d0
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AN211A
Freescale(Motorola) http://www.freescale.com/ Application Note AN211A
Good Stuff
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Depletion Mode FETS
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Enhancement Mode FETs
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Depletion-Enhancement Mode FETs
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MMICs
Monolithic Microwave Integrated Circuit(MMIC) 12 Vdc typical working voltage Impedances 50Ω Noise Figure 3.5 to 6 dB 2 Gound, Input and Output leads
Power feed via Output
In plastic package Circuits employ Microstripline construction
technique
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MSA-0270 MMIC
3db bandwith DC-2.8GHz 12db gain at 1.0GHz http://www.avagotech.com/
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Display Devices
LEDs LCD CRTs Vidicons CCds
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Light Emitting Diodes(LED)
Forward Biased 1.5 to 4.5 volts depending on the material Red Green Yellow Blue Ultraviolet Infrared Working current about 10 to 20 mA Used with current limiting resistor Symbol shows two OUTGOING rays
Photodiodes show incoming rays
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Cathode-Ray Tube(CRT)
Oscilloscopes use higher-precision electrostatic-deflection
Persistence is the length of the image remains on the screen after the beam is turned off
Excessive Anode voltage causes: X-Rays Reduces deflection
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Liquid-Crystal Displays(LCD)
The Crystalline liquid changes the way light is refracted
The consume less power then other displays
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Vidicons and CCDs
Vidicons are CRTs in reverse Magnetic coils are used to scan capacitor cells
The Cells discharge when exposed to light The electron beam recharges them with the
beams current sampled for image data.
Charged-Coupled-Device Stores photoenerated charges as signals
corresponding to pixels DOES NOT perform Analog-to-Digital Convertion
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Poor-Man's Curve Tracer
http://octopus.freeyellow.com/octopus.html
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Manufacturers
http://www.fairchildsemi.com/
http://www.onsemi.com/
http://www.freescale.com/
http://www.analog.com/en/index.html
http://www.microchip.com/
http://www.national.com/
http://www.ti.com/
http://www.avagotech.com/pages/home/
http://www.nxp.com/