AMATEUR RADIO OPERATOR INTRODUCTION January 2013 Active 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
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 TubesTransistorsFETS Charge Source CathodeEmitterSource Control Terminal GridBaseGate Charge Collector Plate (Anode) CollectorDrain ControlVoltageCurrentVoltage
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!!!!!!!!