In this article we will cover Varactor diode, its Symbol, operation, characteristics, advantages and applications.
What is Varactor diode ?
It is a p-n-junction diode, whose internal capacitance can be adjusted by application of reverse bias voltage.
It is controlled by input voltage that means its output voltage depends upon the supplied input voltage. It works in the reversed biased condition and is used to store charges.
A varactor diode is also known as voltcap diode or varicap diode that indicates its varying capacitance.
It is the most highly used semiconductor device in the electronic industry.
Diode is a two terminal semi-conductor device that allows the flow of current in single direction. It is widely used to convert alternating current ( AC ) to direct current ( DC ).
There are many types of diode but they all have similar basic structure i.e a sandwich combination of p-type and n-type material.
Examples : Zener diode, Light Emitting Diode, LASER diode, Schottky diode and varactor diode.
Symbol
The Symbol of varactor diode is similar to p-n-junction diode as it has the same structure. It looks like a diode connected in series with a capacitor. 
In the diagram you can see a diode connected with a parallel line that indicates capacitor and the gap between two parallel line is dielectric.
Operation
We know, diode is made of p-type and n-type semiconductor where the majority charge carriers are holes and electrons respectively.
The sandwich structure of p-type and n-type material creates p-n-junction and the thin layer between the junction is known as depletion layer. The width of depletion layer depends on biasing technique ( forward or reversed biased ).
When we use it in forward biased condition, the depletion region is thin and current flows easily.
when we use it in reversed biased condition, the depletion region becomes broad and block the flow of current.
The varactor is always used in reverse biased condition because it is used to store charge. If we use it in forward biased condition it will store no charge as current can flow easily in this condition.
Varactor diode characteristics
It is made keeping definite C-V curve in mind that can be attained by changing the intensity of doping during manufacturing process.
On the basis of doping type that is either linear doped or non-linear doped, varactor diode can be classified into two types –
-
Abrupt varactor diode
- The diode that exhibits inverse square of the C-V function with constant doping concentration.
-
Hyper-Abrupt varactor diode
- It shows higher capacitance when the voltage gets changed.
Advantages of varactor diode
It has following advantages –
- They area economical and affordable.
- They produce less noise when compared to other diodes.
- They are made compact and light weight.
Applications of Varactor diode
It is used in –
- Small remote control
- Frequency multiplier
- Signal modulation demodulation
- Voltage controlled oscillators
- Parametric amplifiers
- LC circuit or tank circuit
Frequently Asked Questions
- Can we adjust the capacitance of varactor diode manually ?
- The capacitance of varactor diode can be adjusted by adjusting the reverse voltage across its terminals.
Author
Akash Sharma
People also search for –