I hope you all are fine; this is the ninth article in the series on introduction to basic electronic components. In the previous article I have discussed about the Transient Voltage Suppression (TVS) Diode in this article I will discuss the basics of the Varactor Diode.
After reading this post the reader will be able to learn about the basics of the Varactor diode, construction and working of the Varactor diode and finally the applications of the Varactor diode. So sit back, keep reading and enjoy learning.
What is Varactor Diode :
Varactor diode also known as the varicap or tuning is the two terminal passive electronic component which has a variable capacitance. The capacitance of the Varactor Diode depends upon the voltage applied across its ends that is by increasing the voltage across the diode the capacitance decreases. The Varactor diodes are used in voltage controlled oscillators, amplifiers and tuned circuits. The Varactor diode consists of the PN junction and exploits the voltage dependent capacitance of the reverse bias PN junction. The Varactor diode works in the same way as the simple PN junction in a way that the varicap allows the current to flow in one direction and opposes its flow in the other direction. The schematics symbol of the Varactor diode is as shown in the following image:
Construction of the Varactor Diode:
The Varactor Diode is composed of the PN junction thus the basic construction of the Varicap is similar to that of the simple PN junction diode but the PN junction in Varactor diode is optimized for variable capacitance. When one side of the Varactor diode is doped with acceptor ions and the other side with donor ions the PN junction is formed and the electrons from the N-side enters into the P-side and holes from P-side enters into the N-side and leave the charge behind them due to which the depletion region is formed. The basic construction of the Varactor diode is as shown in the following figure:
Working of Varactor Diode:
Before we discuss the working of the Varactor diode let us first discuss the forward biased PN junction and the reverse biased PN junction. It is important to note that when a simple PN junction is not biased that is no voltage is connected across the PN junction. In this situation there exists a capacitance across the junction due to charges in the depletion region. When the PN junction is forward biased the depletion region reduces due to the applied potential difference and as the PN junction is reverse biased the depletion region increases due to the applied potential difference. Thus it is to be noted that the Varactor diode exploits the capacitance of the reverse biased PN junction. The Varactor diode operates in the Reverse Biased condition and as the reverse bias voltage increases the width of the depletion region increases and thus the capacitance reduces. Varying the voltage across the reversed biased Varactor diode alters the capacitance of the diode.
Applications of the Varactor Diode:
Some of the applications of the Varactor are:
- Varactor diode is used in microwave circuits.
- The Varactor diode is used in the amplifier circuits.
- The Varactor diode is also employed in tuning circuits.
- The Varactor diode is also employed in voltage controller circuits.
- The Varactor diode is also used in the LC tank circuits.
Introduction to Varactor Diode
I hope this article would be helpful for you; I have discussed the basics of the Varactor diode in this article. That is all for now in the next article I will come up with more interesting engineering topics. Till then stay connected, keep reading and enjoy learning.