26 March 2018

What is PN junction diode | Symbol | Application | VI characteristics

A P-N junction diode is a silicon. The P-N junction diode is the basic element for semiconductor diodes. One of the terminals is doped with p-type879 material and the other with N-type of material. The schematic symbol shown in the figure, P-N junction diode is made up of P-type silicon and N-type silicon semiconductor materials.

P-N junction diode is used in a variety of applications like LASER, solar cell, LED, digital logic design, DC power supply, etc. This article also gives many more application listed below.

Symbol of PN junction diode :

Symbol of PN junction diode

Application of PN junction diode :
  • Light-emitting diode application
  • Laser
  • It can be also used solar cells
  • It used in the detector as well as the demodulator circuit
  • It is used in many circuit or diode-like, a switching diode, Zener diode, PIN photo-diode, varactor diode
  • It is used as switches in digital logic design
  • It can be also used p-n junction photodiodes
  • It can be used as a rectifier in DC power supply
  • It is also used clipping circuit
  • It can be also used computers, radios, radars as wave shaping circuit
V-I characteristics of PN junction diode :
  • When the anode is positive with respect to the cathode, the diode is to be forward biased. From Vs = 0 to total cut-in voltage, the forward diode current is very small. 
  • Cut in voltage is also known as threshold voltage or called turn-on voltage.
  • For a lower power diode, the current in the forward direction increases first exponentially with voltage and then becomes almost linear.
  • When the cathode is positive with respect to the anode, the diode is said to be reverse biased.
  • In the reverse biased condition, a small reverse current called as a leakage current.
  • The leakage current is almost independent of the magnitude of reverse voltage until this voltage reaches breakdown voltage.
  • At this reverse breakdown, the voltage remains almost constant but reverse current becomes quite high limited only by the external circuit resistance.
  • A large reverse breakdown voltage, associated with high reverse current, so power is lost and maybe diode is destroyed.
  • This shows that the reverse breakdown of a power diode must be avoided by operating it below the specific peak reverse repetitive voltage shown in the figure.

VI characteristics of PN junction diode
V-I characteristics of a P-N junction diode

This article also gives the various types of diode listed below: