2. THE VARACTOR DIODE
• The varactor diode also referred to as Voltacaps ,
Varicaps , VVC (voltage variable capacitance)
diodes.
• It is a semiconductor, voltage dependent and variable
capacitance diode.
3. It operates in reverse biased.
The varactor diode consists of
standared PN junction.
P and N region act as two
plates of capacitor plates.
The depletion region acts as a
capacitor dielectric.
This is exactly same
construction as capacitor.
Its junction capacitance varies
with the amount of reverse
biased voltage.
VARACTOR DIODE
4. BASIC OPERATION
∁ = 𝜀𝐴
𝑑
A is plate area ,d is plate
separation and 𝜀 is the
dielectric constant.
d∝ √v C∝
1
𝑑
C∝
1
√𝑣
Capacitance parameters are
controlled by
1. Doping.
2. Size and geometry of
diode construction.
5. GRAPHICAL ANALYSIS
In this graph the reverse biased voltage ranges from
(1-30v).
Capacitance ranges from 30pf to slightly less then 4pf
As V become higher the decrease in capacitance
become smaller.
6.
7. APPLICATIONS
Varactor diodes are widely used in electronic industry.
They are used in applications where a voltage controlled variable
capacitance is required.
They are used in
1. Voltage controlled oscillators
2. Parametric amplifiers
3. Frequency multipliers
4. FM modulator