05-Semiconductors and Display Devices

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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/