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PN Junction Diode
ENGI 242ELEC 222
January 2004 ENGI 242/ELEC 222 2
PN Junction Diode• Diode Model Analysis
– Ideal– Approximation– Exact
• Diode Specification Sheets• Diode Resistance
– Static Resistance RD
– Dynamic Resistance rd
– Average Resistance rdav
• Diode Characteristic Curves• Simulation
January 2004 ENGI 242/ELEC 222 3
Ideal diode: (a) symbol; (b) characteristics.
January 2004 ENGI 242/ELEC 222 4
Conduction state of the ideal diode based on the applied bias
January 2004 ENGI 242/ELEC 222 5
Typical Diode Curves
January 2004 ENGI 242/ELEC 222 6
Forward Bias Curve is Exponential
January 2004 ENGI 242/ELEC 222 7
Diode Response vs Temperature
January 2004 ENGI 242/ELEC 222 8
Semiconductor Diode Characteristics
D
K
kV
TD S
D
S
K
I = I (e - 1)
I = Diode Current
I = Reverse Saturation Current
T = Temperature Kelvin
January 2004 ENGI 242/ELEC 222 9
Determining the dc Resistance
January 2004 ENGI 242/ELEC 222 10
rd - the Dynamic (ac) Resistance
January 2004 ENGI 242/ELEC 222 11
Determining rd - the ac Resistance at Q
January 2004 ENGI 242/ELEC 222 12
Determining rd - the ac Resistance
January 2004 ENGI 242/ELEC 222 13
rdav – the Average ac Resistance
Draw line through 2 points +VP and -VP
January 2004 ENGI 242/ELEC 222 14
Circuit to display the V - I characteristics
January 2004 ENGI 242/ELEC 222 15
PSpice Model Editor – D1N914 Parameters
January 2004 ENGI 242/ELEC 222 16
DC Sweep Simulation Settings
January 2004 ENGI 242/ELEC 222 17
PSpice plot of forward bias at 25°C
January 2004 ENGI 242/ELEC 222 18
DC Sweep Simulation Settings
Note First select Edit Pspice Model, and change IBV to 10
January 2004 ENGI 242/ELEC 222 19
PSpice generated plot characteristics at 25°C
This Probe output shows both forward and reverse breakdown
January 2004 ENGI 242/ELEC 222 20
PSpice Netlist Output Part 1
January 2004 ENGI 242/ELEC 222 21
PSpice Netlist Output Part 2
Diode Circuit Analysis
ENGI 242ELEC 222
January 2004 ENGI 242/ELEC 222 23
Diode Circuit Analysis• Diode Circuit Analysis
– Graphical Analysis using Loadlines– Analytical Analysis using KVL and KCL
• LEDs• Zener Diodes• Diode Resistance
– Static Resistance RD
– Dynamic Resistance rd
– Average Resistance rdav
• Diode Characteristic Curves• Simulation
January 2004 ENGI 242/ELEC 222 24
Series Diode Configuration
January 2004 ENGI 242/ELEC 222 25
Drawing a Load Line to Find the Q Point .
January 2004 ENGI 242/ELEC 222 26
Diode Circuit and Characteristics .
January 2004 ENGI 242/ELEC 222 27
Load Line Example
January 2004 ENGI 242/ELEC 222 28
Determining the Unknown Network Quantities
January 2004 ENGI 242/ELEC 222 29
Network Example
January 2004 ENGI 242/ELEC 222 30
Determining the Unknown Network Quantities
January 2004 ENGI 242/ELEC 222 31
Network Example
January 2004 ENGI 242/ELEC 222 32
Zener Diode Equivalents
January 2004 ENGI 242/ELEC 222 33
Basic Zener Regulator
January 2004 ENGI 242/ELEC 222 34
Determining the State of the Zener
January 2004 ENGI 242/ELEC 222 35
The Zener Equivalent Circuit Operation
January 2004 ENGI 242/ELEC 222 36
Zener Diode Regulator
January 2004 ENGI 242/ELEC 222 37
Determining V for the Regulator
January 2004 ENGI 242/ELEC 222 38
Q-Point for the Network
January 2004 ENGI 242/ELEC 222 39
Network in the conducting state
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