PIN Diodes

Authors:

Published On:

Sep 5, 2011

Last Updated:

Jul 16, 2022

A PIN diode is a semiconductor diode with a wide un-doped intrinsic semiconductor region between a p-type and n-type semiconductor region (hence the name PIN).

A photo of a small, through-hole PIN diode.

A “normal” PN diode has a very small intrinsic region, which is good when you wish to use the diode as a standard rectifier. The PIN diodes wide intrinsic region makes it an inferior rectifier, but makes it suitable for¹:

Attenuators
Fast switches
Photodetectors (when used in a reversed-biased state)

Important Parameters

Dark Current

Symbol: $I_D$
Units: $nA$

Typically in the 0.1-5nA range.

Extinction Ratio

Field of View

Symbol: FoV

Output Rise Time

Symbol: $t_r$
Units: $s$

Responsivity

Symbol: $A/W$

PIN diodes are normally operated in the reverse bias state.

Because of their good light-to-current linearity, they are commonly connected to a transimpedance amplifier (one which converts an input current into an output voltage). A typical example would be the Maxim MAX3658, which is designed for fibre-optic applications.

RF Applications

PIN diodes act as almost perfect resistors in the RF and microwave frequencies¹. The resistivity these AC waveforms see is dependent on the DC bias current flowing through the diode, and the intensity, wavelength and modulation rate of the incoming light.

Because the PIN diodes RF resistance is dependant on the DC bias current, they can be used as an RF switch or variable resistor. The RF resistance can range from about $100m\Omega$ to $10k\Omega$ .

Reverse Recovery Time

PIN diodes have a very poor reverse recovery time.

Wikipedia. PIN diode. Retrieved 2021-11-25, from https://en.wikipedia.org/wiki/PIN_diode. ↩ ↩²