Semiconductor devices - Photodiode
Semiconductor device tutorial
Semiconductor devices - Photo diode
A photodiode is a PN junction diode that conducts current when exposed to light. This diode is actually designed to operate in reverse bias mode. This means that the greater the intensity of the falling light, the greater the reverse bias current will be.
The following figure shows a schematic symbol and construction detail of a photodiode.
How a photo diode works
It 's a reverse biased diode . The reverse current increases as the intensity of the incident light increases. This means that the reverse current is directly proportional to the intensity of the falling light.
It consists of a PN junction mounted on a P-type substrate and sealed in a l case.tion consists of a transparent lens and it is the window where the light is supposed to fall.
As we know, when the PN junction diode is reverse biased, a very small amount of reverse current flows. The reverse current is thermally generated by electron-hole pairs in the depletion region of the diode.
When light falls on the PN junction, it is absorbed by the junction. This will generate more electron-hole pairs. Or we can typically say that the amount of reverse current increases.
In other words, as the intensity of the falling light increases, the resistance of the PN junction diode decreases.
- This action makes the diode more conductive.
- These diodes have a very fast response time
- They are used in high-performance computing devices.
- It is also used in alarm circuits, circuitscount cooked, etc.