A Pin diode is a special type of diode that contains an undoped intrinsic semiconductor between the p-type semiconductor and n-type semiconductor regions. It differs from a normal diode in the sense that it has an extra layer in between the p and the n junctions. Forward biased operation of PIN Diode When the PIN diode is subjected to forward bias, the depletion region at the p-n junction reduces. With the reduction of the depletion region, current starts flowing through the diode. The PIN diode acts as a variable resistance when operated in forward bias. A high electric field is developed across the junction and this, speeds up the transport of charge carriers from the P region to the N region. This helps in faster operation and therefore pin diode is used for high-frequency applications. Reverse biased operation of PIN Diode When the pin diode is in reverse biased condition, the width of the depletion region increases. At a certain reverse bias voltage, the entire intrinsic layer will be swept out of charge carriers. This voltage is called the swept in voltage. The value is -2v. It is used for switching purposes while in reverse bias.
