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