Transcript Diodes - RPI ECSE - Rensselaer Polytechnic Institute

SMART LIGHTING
Diodes
K. A. Connor
Mobile Studio Project
Center for Mobile Hands-On STEM
SMART LIGHTING Engineering Research Center
ECSE Department
Rensselaer Polytechnic Institute
Intro to ECSE Analysis
Outline
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Diodes – What is their basic function?
Current flows one way.
How Stuff Works – RPI Connection
PN Junction
Diode I-V Characteristic
LEDs
K. A. Connor
15 September 2015
Diodes
D1
ANODE
CATHODE
DIODE
• A diode can be considered to be an
electrical one-way valve.
• They are made from a large variety of
materials including silicon, germanium,
gallium arsenide, silicon carbide …
K. A. Connor
15 September 2015
Diodes
• In effect, diodes act like a flapper valve
• Note: this is the simplest possible model of a
diode
K. A. Connor
15 September 2015
Diodes
• For the flapper valve, a small positive pressure is
required to open.
• Likewise, for a diode, a small positive voltage is
required to turn it on. This voltage is like the
voltage required to power some electrical device.
It is used up turning the device on so the voltages
at the two ends of the diode will differ.
• The voltage required to turn on a diode is typically
around 0.6-0.8 volt for a standard silicon diode and a
few volts for a light emitting diode (LED)
K. A. Connor
15 September 2015
Diodes
D1
D1N4002
VAMPL = 10V
V1
R1
FREQ = 1k
1k
0
• 10 volt sinusoidal voltage source
• Connect to a resistive load through a diode
• This combination is called a half-wave rectifier
K. A. Connor
15 September 2015
Diodes
VAMPL = 10V
Sinusoidal Voltage
V1
FREQ = 1k
10V
5V
0V
-5V
-10V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
V(D1:1)
Time
K. A. Connor
15 September 2015
Diodes
D1
VAMPL = 10V
V
V1
D1N4002
Half-wave rectifier
V
R1
FREQ = 1k
1k
0
10V
5V
0V
-5V
-10V
0s
0.5ms
V(D1:1)
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
V(D1:2)
Time
K. A. Connor
15 September 2015
How Stuff Works: LEDs
K. A. Connor
15 September 2015
A Little History
Note The
Former
Name!
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15 September 2015
PN Junction
At the junction, free
electrons from the N-type
material fill holes from the
P-type material. This
creates an insulating layer
in the middle of the diode
called the depletion zone
K. A. Connor
15 September 2015
PN Junction
When the negative
end of the circuit is
connected to the
n-Type layer & the
positive end to the
p-Type, electrons
& holes move, the
depletion zone
disappears &
current flows
K. A. Connor
15 September 2015
PN Junction
When connected in
the other direction,
electrons collect on
one end and holes
on the other and the
depletion zone
grows
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15 September 2015
Diode I-V Characteristic
• For ideal diode, current flows only one way
• Real diode is close to ideal
Ideal Diode
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15 September 2015
LED
• Advantages?
• Differences from
other diodes?
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Today
15 September 2015
LED
• Wikipedia
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15 September 2015
LED I-V Characteristics
• LED Tutorial
• Linear LED Calculator
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15 September 2015