Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone...

13
Diodes Networks and Embedded Software Module 3.1.1 by Wolfgang Neff

Transcript of Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone...

Page 1: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Diodes

Networks and Embedded Software

Module 3.1.1

by Wolfgang Neff

Page 2: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Semiconductors (1)

• Classification

– Conductor

• Silver, copper

• High conductivity

– Insulator

• Porcelain, plastics

• High resistivity

– Semiconductor

• Silicon, germanium

9/26/2018 Module 3.1.1 – Diodes 2

Elec

tric

al R

esis

tivi

ty ρ

[Ωcm

]

Semiconductors10

104

kΩcm

Conductors10-6

10-5

μΩcm

Insulator

1010

1020

GΩcm

Page 3: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Semiconductors (2)

• Conductivity (simple model)

Free electrons

Conductor

Tightly bound electrons

Insulator

Loosely bound electrons

Semiconductor

9/26/2018 Module 3.1.1 – Diodes 3

Page 4: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Semiconductors (3)

• Conductivity (band model)

9/26/2018 Module 3.1.1 – Diodes 4

Conduction band

Valence bandEner

gy

Conductor

Conduction band

Valence bandEner

gy

Semiconductor

Tiny energy gap

Conduction band

Valence band

Ener

gy

Insulator

Huge energy gap

Overlap

Page 5: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Semiconductors (4)

• Intrinsic conduction

– Semiconductors are insulators

– Electrons can cross the energy gap

– Heat can provide this energy.

– Conductivity depends on temperature

9/26/2018 Module 3.1.1 – Diodes 5

Conduction band

Valence bandEner

gy

Semiconductor

Semiconductors are NTC. The hotter the

conductiver.

Page 6: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Doping (1)

• Donors

– Some atoms replaced by donors

– Extra electrons

– Better conductivity

– N-type doping

9/26/2018 Module 3.1.1 – Diodes 6

N-typesemiconductor

Donor

Free extra electron

Page 7: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Doping (2)

• Acceptors

– Some atoms replaced by acceptors

– Lack of electrons

– Better conductivity

– P-type doping

9/26/2018 Module 3.1.1 – Diodes 7

P-typesemiconductor

Acceptor

Hole acts as positive charge

Page 8: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Doping (3)

• P–n junction

– Electrons migrate into holes

– No free charges in depletion zone

– Depletion zone is insulating

9/26/2018 Module 3.1.1 – Diodes 8

P-type semi-conductor

N-type semi-conductor

Depletion region(insulating)

P-type semi-conductor

N-type semi-conductor

Page 9: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Doping (4)

• P–n junction (continued)

• Power supply

– P-type side: –

– N-type side: +

• Depletion zone larger

• Insulation remains

9/26/2018 Module 3.1.1 – Diodes 9

P-type semi-conductor

N-type semi-conductor

Depletion regionDepletion region

N-type semi-conductor

P-type semi-conductor

Page 10: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Doping (5)

• P–n junction (finished)

• Power supply

– P-type side: +

– N-type side: -

• Depletion zone smaller

• Insulation diminishes

9/26/2018 Module 3.1.1 – Diodes 10

P-type semi-conductor

N-type semi-conductor

Depletion region

N-type semi-conductor

P-type semi-conductor

Page 11: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Diodes (1)

• P–n junctions are diodes

– Flow Control Valve

• One-Way Road

– Forward

• P-type: +, n-type: -

• Current flows

– Reverse

• P-type: -, n-type: +

• Current gets blocked

9/26/2018 Module 3.1.1 – Diodes

Electric current flows

p-type n-type+ -

Electric current is blocked

p-type n-type- +

11

Page 12: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Diodes (2)

• Example: 1N4148

– Maximum forward current

• IF = 300 mA

– Maximum reverse voltage

• VR = 100 V

– Reverse Leakage

• IR = 0.025 μA (VR = 20 V)

• IR = 5.0 μA (VR = 70 V)

9/26/2018 Module 3.1.1 – Diodes

Forward

+ -

p-type n-type

Anode Cathode

Reverse

- +

12

Page 13: Diodesneff.site/courses/nwes/nwes_3/1.1_script.pdf · holes –No free charges in depletion zone –Depletion zone is insulating 9/26/2018 Module 3.1.1 –Diodes 8 P-type semi-conductor

Diodes (3)

• Applications

– Reverse voltage protection

– Rectifier

9/26/2018 Module 3.1.1 – Diodes

~ UAC

- UDC(not really)

13

+ -+ -device

- ++ -device