The varactor diode is a semiconductor device that has a voltage-dependent variable capacitance. It consists of a standard PN junction with a depletion region that acts as a dielectric between the P and N regions, which form the capacitor plates. As the reverse bias voltage is increased, the depletion region width increases, reducing the capacitance according to the formula C∝1/√v. Varactor diodes are used in applications like voltage controlled oscillators, parametric amplifiers, and frequency multipliers that require a voltage-controlled variable capacitance.

1. VARACTOR DIODE

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.

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