Types of Photo-diode
- PN photo-diode
- Schottky photo Diode
- PIN photo-diode
- Avalanche Photo-diode
Important features of Photo-diode are following:
- It can turn its current ON and OFF in nanoseconds. It is one of the fastest photo detectors.
- Operational sound is low
- Conversion from light energy to electrical energy is precise
- Robust construction and long life
Construction of Photo-diode
P-type and N-type semi-conductor are diffused then ohmic junction (has some resistance) formed. Above this junction a lens has been used in the cap of the unit to focus maximum light on junction. It is mounted on TO-5 packages and has active diameter of 2.5 mm.
Working of Photo-diode
When light energy strikes on lens of the photo-diode. Lens concentrates light on ohmic junction due to which electrons and holes are generated at junction, because of this the resistance of junction decreases. Then, holes of the region start move toward the anode, and electrons move toward the cathode which generates photo-current.