AMATEUR RADIO OPERATOR

INTRODUCTION

January 2013Active Devices

Diodes, Transistors, and Tubes

AGENDA Diodes TRANSISTORS/FETS TUBES QUESTIONS

SEMICONDUCTORS VERY STABLE CRYSTAL STRUCTURE SILICON & GERMANIUM MOST COMMON SILCON ATOMS SHARE VALENCE

ELECTRONS (8 ELECTRONS) CAN BE GOOD INSULATOR INTRINSIC- PURE MATERIAL, NO FREE

CHARGE CARRIERS EXTRINSIC – MATERIAL DOPED WITH

EXTRA CARRIERS

DOPING

JUNCTIONS N TYPE – EXTRA

ELECTRON (- CHARGE) P TYPE – MISSING

ELECTRON (+ CHARGE)

PN JUNCTION

DEPLETION ZONE

DEPLETION ZONE

PN JUNCTION

FORWARD BIAS

DIODES 2 TERMINAL PN

JUNCTION ANODE – P CATHODE - N

Diodes (i-v curves)

Diodes

DIODE APPLICATIONS SWITCH RECTIFICATION DEMODULATION REGULATION LIGHT EMITTING (LED)

RECTIFIERS

ZENER DIODES

Used to regulate voltages

Behaves normally when forward biased

When reversed biased, non destructive voltage breakdown

ZENER Voltage

ZENER Regulation

TRANSISTORS 3 TERMINAL DEVICE 2 JUNCTIONS P-N-P N-P-N ALSO KNOWN AS

“BIPOLAR TRANSISTOR”

BASE CURRENT CONTROLS EMITTER/COLLECTOR CURRENT

NPN TRANSISTOR

PNP TRANSISTOR

FIELD EFFECT TRANSISTOR TWO TYPES

JUNCTION FIELD EFFECT or JFET METAL OXIDE SILICON FIELD EFFECT or

MOSFET A CONDUCTIVE CHANNEL WITH 2

JUNCTIONS N-CHANNEL P-CHANNEL

FETS

TRANSISTOR - FET EMITTER, BASE,

COLLECTOR FOR BIAS INCREASES

CURRENT CURRENT CONTROLS LOW INPUT Z

SOURCE, GATE, DRAIN REV BIAS DECREASES

CURRENT VOLTAGE CONTROLS HIGH INPUT Z

VACUUM TUBES Developed in late

1800’s and early 1900’s Still used in

applications requiring high power or high voltages (power amplifiers)

Tube Construction Thermionic emission Filament (Heater) used to heat cathode Cathode made of tungsten and thorium Heated cathode emits an electron cloud Positive potential placed on Plate (Anode) to

attract electrons Negative potential Grid used to control

electron flow

Vacuum Diode

Vacuum Triode

Tubes – Take Aways Grid current – minimal or zero as long as

Grid is negative relative to cathode Grid is usually a mesh Grid is closer to cathode Heater is farthest from Plate Used in high power applications Inside of envelope is a vacuum

Tubes, transistors, FETS

Tubes Transistors FETS

Charge Source Cathode Emitter Source

Control Terminal Grid Base Gate

Charge Collector

Plate (Anode) Collector Drain

Control Voltage Current Voltage

AMPLIFICATION Produce an output which is an enlarged

reproduction of the input. Device is called an AMPLIFIER An accurate reproduction is called “LINEAR” Imperfections in reproduction are called

“DISTORTION” Tubes, Transistors, and FETs can all be

amplifiers. Typically gain is measured in dB

Amplifier Applications AF (Audio Frequency) RF (Radio Frequency) IF (Intermediate Frequency) PA (Power Amplifier)

Current, Voltage and or Power can all be amplified

Distortion

Homework Review Class Notes and Handouts

Read ahead for next week

QUESTIONS????

THANK YOU!!!!!!!!