EE292 Spring2015 Ch10 Diodes Suplemental Em

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Electrical Engineering: Principles and Applications, 6eAllan R. Hambley

Copyright ©2014 by Pearson Education, Inc.All rights reserved.

EE292CHAPTER 10 DIODESSupplemental Info

Contains information from internet websites,for EE292 class reference only





EE292Chapter 10 References

Various Diodes and Applications

1. Light Emitting Diodes (LED)

2. Photodiodes

3. Silicon Controlled Rectifier (SCR)

4. Triac

5. Term project ideas?





EE292

4/11/2006 BAE 5413 3

Diode devices

• Check valve behavior

Diffusion at the PN junctionof P into N and N into Pcauses a depleted non-conductive region

Depletion is enhanced byreverse bias

Depletion is broken down byforward bias

• When forward biased

High current flow junctionvoltage

• When reverse biased

Very low current flow unlessabove peak inverse voltage(PIV) (damaging torectifying diodes, OK forzeners)

D1

cathode

-

anode

+

+ -

Depletion region

1N412

Diode

Schematic Symbol

Semiconductor

Elements

Typical

Component

Appearance

P -

doped

N -

doped

Breakdown

voltage

(PIV)

V

I

Junction

Voltage

0.7 - silicon

0.3 - germanium

Forward

bias

current

Reverse

bias

current





EE292Light Spectrum

Red, green and blue LEDs





EE292

When a light-emitting diode is forward biased,

electrons are able to recombine with holes within the device, releasing energy in the form

of photons.

This effect is called electroluminescence and

the color of the light (corresponding to theenergy of the photon) is determined by the

energy gap of the semiconductor.

LED Light Emitting Diodes

Source http://en.wikipedia.org/wiki/Light-emitting_diode

http://en.wikipedia.org/wiki/Electrons

http://en.wikipedia.org/wiki/Electron_hole

http://en.wikipedia.org/wiki/Photon

http://en.wikipedia.org/wiki/Electroluminescence

http://en.wikipedia.org/wiki/Energy_gap

http://upload.wikimedia.org/wikipedia/commons/6/62/Br20_1.jpg

http://en.wikipedia.org/wiki/Energy_gap

http://en.wikipedia.org/wiki/Electroluminescence

http://en.wikipedia.org/wiki/Photon

http://en.wikipedia.org/wiki/Electron_hole

http://en.wikipedia.org/wiki/Electrons







EE292

Deep UV LED for SpaceApplications





EE292

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Semicoductor Quantum Devices

• Absorption of a photon of sufficient energy

elevates an electron into the conduction bandand leaves a hole in the valence band.

• Conductivity of semi-conductor is increased.

• Current flow in the semi-conductor is

induced.

•

External circuit to read out the current

Conduction band

Energy gap

Valence band

Energy

level

+

-

Photon

(hv)

Hole

Electron

n- region

p+ Active AreaInsulation

Depletion region

Back Metalization

n+ Back Diffusion

Front

Contact

Rear

Contact

Incident light

Absorbtion in the

depletion layer

causses current to

flow across the

photodiode and if

the diode isreverse biased

considerable

current flow will be

induced





EE292

4/11/2006 BAE 5413 9

Photodiode fundamentals

• Based on PN or PIN junction diode

photon absorption in the depletion

region induces current flow

Depletion layer must be exposed

optically to source light and thick

enough to interact with the light

• Spectral sensitivity

Material Band gap

(eV)

Spectral sensitivity

silicon (Si) 1.12 250 to 1100 nm indium arsenide

(InGaAs)

~0.35 1000 to 2200 nm

Germanium (Ge) .67 900 to 1600 nm

I

P

N

+

-

h

RL

IL

electron

hole





EE292

4/11/2006 BAE 5413 10

Photodiode characteristics

• Circuit model

– I0 Dark current (thermal) – Ip Photon flux related current

• Noise characterization

Shot noise (signal current related)

– q = 1.602 x 10 –19 coulombs

– I = bias (or signal) current (A)

– is = noise current (A rms)

Johnson noise (Temperature related)

– k = Boltzman’s constant = 1.38 x 10 –23 J/K

– T = temperature (°K)

– B = noise bandwidth (Hz) – R = feedback resistor (W)

– eOUT = noise voltage (Vrms)

qii s 2

kTBReout 4

Ip Rj Cj

Rs

I0





EE292

4/11/2006 BAE 5413 11

Photodiode current/voltagecharacteristics

Isc (light level dependent)

Current

V o l t a g e

Increasing Light level

Dark current

P ho t o c o nd u c t i v e m o d e l o ad l i ne

P ho t o v o l t ai c m o d e l o ad l i ne





EE292

4/11/2006 BAE 5413 12

Trans-impedance amplifierfunction

• Current to voltage converter (amplifier)

• Does not bias the photodiode with a voltage as current

flows from the photodiode (V 1 = 0)

•

Circuit analysis

s f I I

0o I

01 V

s f f f f I R I RV +

-

+

-

Is

Vout

Vf

Io

+

If V

1

s f f out I RV V

–Note: current to voltage conversion





EE292

4/11/2006 BAE 5413 13

Diode operating modes

•

Photovoltaic mode Photodiode has no bias voltage

Lower noise

Lower bandwidth

Logarithmic output with light intensity

• Photoconductive mode

Higher bandwidth

Higher noise

Linear output with light intensity

+

-

+

-

Vout

+

-

+

-

VoutVs

-





EE292 Solar Zone & Photovoltaics

http://upload.wikimedia.org/wikipedia/commons/0/0b/Sasc2010_tokai_challenger_table_mountain.jpg





EE292 Photovotaic System In Power Grids





EE292Silicon Controlled RectifierMore control than rectification

http://en.wikipedia.org/wiki/File:SCR.JPG

http://en.wikipedia.org/wiki/File:Thyristor_circuit_symbol.svg





EE292 Triac: Bidirection SCR

http://en.wikipedia.org/wiki/File:Triac_funktion.gif

http://upload.wikimedia.org/wikipedia/commons/8/81/Triac_Quad_I_like_SCR.JPG

http://upload.wikimedia.org/wikipedia/commons/d/d1/Triac.svg



Electrical Engineering: Principles and Applications, 6eAll R H bl

Copyright ©2014 by Pearson Education, Inc.All i ht d

EE292 How to Connect a LED:

•

Requires 1.5~2.5V and 10 mA• To prevent overloading, use resistor 470 Ω

Documents

EE292 Spring2015 Ch10 Diodes Suplemental Em