Photodiodes
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Overview
A photodiode is a two terminal component which converts light into an electrical current. Just like a general-purpose diode, they consist of a normal semiconductor PN junction. The difference is the photodiodes semiconductor junction is exposed to light through a transparent window rather than encapsulated in opaque material as in a standard diode.
Uses:
- Light sensors
- MOSFET gate drivers in opto-couplers
Schematic Symbol
Below is the common schematic symbol used for a photodiode:
![](/assets/images/photodiode-schematic-symbol-35915516ff267023e1022ceab0ffe283.png)
tip
The photodiode schematic symbol is very similar to one for an LED (light-emitting diode), but the "light arrows" on an LED point away from the diode.
Types of Photodiodes
There are three basic types of photodiode:
- PN junction photodiode
- PIN photodiode
- Avalanche photodiode