ELIZABETHTOWN COMMUNITY AND TECHNICAL COLLEGE
BEX 100 BASIC ELECTRICITY FOR NON MAJORS
LECTURE GUIDE – SEMICONDUCTORS - DIODES
Instructor: Jerry Brown
Reference: Delmar’s Standard Textbook of Electricity, Third Edition
DIODES
Objectives
1. Understand the materials that make up the basic diode
2. Describe the basic function of the diode
3. Define the different types of diodes and understand their operating
principles
4. Identify schematic symbols representing the different types of diodes
5. Describe the various applications for diodes
Introduction
Semiconductors –
Class of materials between insulators and conductors
Selenium, copper oxide, gallium arsenide
Silicon & Germanium are most common
Many diodes are made from silicon and germanium
Semiconductors
Tight crystal molecular structure
Must be “doped” to be used to make diodes
“Doping” is adding another material to molten semiconductor
Doping with phosphorus results in N- type material
Doping with boron results in P- type material
Applying voltage to “doped” silicon crystal
Diodes
Unidirectional current flow (Electronic “check valve”)
Schematic symbol indicates direction
Flow from Anode to Cathode
Applications
Rectification
Circuit Control
Clamping Protection
Integrated Types
Forward Bias Connection
Connect positive to “P-“ Material and negative to “N-“
Reverse Bias Connection
Reverse polarity of the voltage connection
Diode Operating Principles
Forward biased – current flow
Reverse biased – no current flow
Diode Rectifiers
Principles Full wave rectifiers
Half wave rectifiers
Diode Leakage Current
Zener Diodes
Designed for “reverse bias” current flow at a specific voltage
Used in “Control Circuits”
Clamping Diodes
Protect circuits from “surge currents”
LED’s (Light Emitting Diodes)
Contains small “window” to allow light to escape when forward biased
Testing Diodes
DVOM has “Diode Test” setting – higher voltage on leads
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