Author: Rufus P. Turner
Published by Howard W. Sams & Co., Inc., Indianapolis, Indiana
Printed in the United States of America
Year of publication: 1966
What are varactor / varicap diodes?
Varactor or varicap diode is a special diode that has the characteristic of modifying its internal capacity as the voltage applied to the terminals varies. The advantage of the varivap diode (varactor) over a trimmer or a variable capacitor is that we can make very fine adjustments and we can get even very small capacities.
Each varicap diode is built to accept a well-defined maximum voltage (12V, 25V, 23V or so). To make the floor of an oscillator more stable (LC circuit), it is preferred to mount the varicap diodes (varactor) at the ends of the control coils.
Children a varicap diode (or capacitive diode) replaces a variable capacitor and we can make oscillators or resonant circuits much more stable.
The varicap diode (varactor) is a reverse polarized diode in which the passage area around the PN junction behaves like a capacitor with variable electrical capacity. This is possible because the passage area consists of two electrically charged layers with opposite electric charges (ions that appear in the two semiconductors). Changing the reverse voltage applied to the diode changes the thickness of the passage area, so it changes the electrical capacity of the diode.
The structure of the paper
CHAPTER 1 - BASIC VARACTOR THEORY
- What Is a Varactor?
- Fundamental Semiconductor Varactor
- The PN Junction
- Junction Operation-Inside The Varactor
- Varactor Ratings
- Types of Varactors
CHAPTER 2 - VARACTOR OPERATION
- Voltage and Current Response
- Multiple Operation
- Varactor and Conventional Capacitor in Combination
- Varactor Tuned Circuits
- Varactor As Frequency Multiplier
CHAPTER 3 - RECEIVING APPLICATIONS
- Tuning Requirements and Considerations
- Automatic Frequency
- Control-RF Amplifier (Preselector)
CHAPTER 4 - TRANSMIT APPLICATIONS
- Tank Tuning
- Frequency Multipliers
- Frequency Modulation
- Amplitude Modulation
- RF Output Control
CHAPTER 5 - VARACTOR AMPLIFIERS
- Basic Principles
- Resonant-Slope
- Amplifiers
- Parametric Amplifier
- DC Amplifier
CHAPTER 6 - INSTRUMENT APPLICATIONS
- Absorption Wavemeter
- Remote Tuned Field-Strength Meter
- Harmonic Intensifier for Frequency Standard
- RF Sweep Oscillator
- Signal Converter
- Electronic DC Voltmeter
CHAPTER 7 - SUPPLEMENTARY APPLICATIONS
- Frequency Divider
- Microwave Limiter
- Wave Filters
- Voltage Tuned Pi Network
- Balanced Modulator
- Ultrahigh Resistance Switch
- Capacitive Potentiometer
- Light-Controlled Capacitor
- Negative Reactor
- Varactor Effects in Conventional Diodes
sources:
Varicap diode. Radio frequency course for beginners
