PIN Diode Basics, Working and Applications

The PIN-diode is an alteration of the PN-junction for particular applications. After the PN-junction diode was developed in the year 1940s, the diode was first exercised as a high-power rectifier, low-frequency during the year 1952. The occurrence of an intrinsic layer can significantly increase the breakdown voltage for the application of high-voltage. This intrinsic layer also offers exciting properties when the device operates at high frequencies in the range of radio wave and microwave. A PIN diode is a one kind of diode with an undoped, wide intrinsic semiconductor region between a P-type and N-type semiconductor region. These regions are normally heavily doped as they are used for Ohmic contacts.The wider intrinsic region is indifference to an ordinary p–n diode. This region makes the diode an inferior rectifier but it makes it appropriate for fast switches,attenuators, photo detectors and high voltage power electronics applications.

Outline of PIN Diode Chip
Outline of PIN Diode Chip

What is a PIN Diode?

The PIN diode is a one type of photo detector, used to convert optical signal into an electrical signal. The PIN diode comprises of three regions, namely P-region, I-region and N-region. Typically, both the P and N regions are heavily doped due to they are utilized for Ohmic contacts.The intrinsic region in the diode is in contrast to a PN junction diode. This region makes the PIN diode an lower rectifier, but it makes it appropriate for fast switches, attenuators, photo detectors and applications of high voltage power electronics.

PIN Diode
PIN Diode

Structure and Working of PIN Diode

The term PIN diode gets its name from the fact that includes three main layers. Rather than just having a P-type and an N-type layer, it has three layers such as

  • P-type layer
  • Intrinsic layer
  • N-type layer

The working principle of the PIN diode exactly same as a normal diode. The main difference is that the depletion region, because that normally exists between both the P & N regions in a reverse biased or unbiased diode is larger. In any PN junction diode, the P region contains holes as it has been doped to make sure that it has a majority of holes. Likewise the N-region has been doped to hold excess electrons.

Structure of PIN Diode
Structure of PIN Diode

The layer between the P & N regions includes no charge carriers as any electrons or holes merge As the depletion region of the diode has no charge carriers it works as an insulator. The depletion region exists within a PIN diode, but if the PIN diode is forward biased, then the carriers come into the depletion region and as the two carrier types get together, the flow of current will starts.

When the PIN diode is connected in forward biased, the charge carriers are very much higher than the level of intrinsic carrier’s attention. Due to this reason the electric field and the high level injection level extends deeply into the region. This electric field assists in speeding up of the moving of charge carriers from P to N region, which consequences in quicker operation of the PIN diode, making it an appropriate device for high frequency operations.


Applications of PIN Diodes

The applications of PIN mainly include the following areas

  • The PIN diode is used as a high voltage rectifier. The intrinsic layer in the diode offers a partition between the both the layers, permitting higher reverse voltages to be tolerated
  • The PIN diode is used as an ideal radio frequency switch. The intrinsic layer among the P & N layers increases the space between them. This also reduces the capacitance between both the regions, thus raising the level of isolation when the PIN diode is reverse biased.
  • The PIN diode is used as a photo detector to convert the light into the current which takes place in the depletion layer of a photo diode, rising the depletion layer by inserting the intrinsic layer progresses the performance by increasing the volume in where light change occurs.
  • This diode is an ideal element to give electronics switching in applications of electronics. It is mainly useful for RF design applications and also for providing the switching, or an attenuating element in RF  attenuators and RF switches. The PIN diode is capable to give much higher levels of consistency than RF relays that are frequently the only other alternative.
  • The main applications of the PIN diode are discussed in the above, although they can also be applied in some other areas

PIN Diode Characteristics

The PIN diode characteristics include the following

This obeys the typical diode equation for small frequency signals. At higher frequencies, PIN diode appears like an approximately perfect resistor. There is a set of stored charge in the intrinsic region. At small frequencies, the charge can be detached and the diode switched OFF.

At higher frequencies, there is not sufficient time to eliminate the charge, so the PIN diode never switched OFF. The diode has a reduced reverse recovery time. A PIN diode properly biased, therefore performs as a variable resistor. This high-frequency resistance may differ over a broad range (from 0.1 Ω-10 kΩ in some cases; the practical range is slighter, though).

The wider intrinsic area also means the PIN diode will have a low capacitance when reverse-biased. In this diode, the depletion region exists completely in the intrinsic region. This depletion region is much better than in a PN-diode, and nearly constant-size, independent of the reverse bias applied to the PN-diode.

This increases the amount where pairs of electron-hole can be produced by an occurrence photon. Some photo detector devices like photo transistors and PIN photodiodes employ a PIN-junction in their construction.

The design of the PIN-diode has some design tradeoffs. Rising the magnitudes of the intrinsic region permits the diode to appear like a resistor at minor frequencies. It harmfully affects the time required to switch off the diode & its shunt capacitance. Therefore, it is essential to choose a device with the most suitable properties for a particular use

Thus, this is all about PIN diode basics, working and applications. We hope that you have got a better understanding of this concept or to implement any electrical and electronic projects, please give your valuable suggestions by commenting in the comment section below. Here is a question for you, what is the function of PIN diode?

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