Why photodiode is operated in reverse bias?
- n the absence of light, the dark current flowing through the diode is of the order of few mA.
- In the presence of light, the photocurrent flowing through the photodiode is slightly increased and it is also in the order of few mA.
- But the change in dark current to photocurrent is not significantly noticeable.
- Therefore, the photodiode is not operated in forward bias condition.
- In the absence of light, the dark current flowing through the photodiode in reverse bias condition is the reverse saturation current and it is very small in magnitude about few nA.
- In the presence of light, the photo current flowing through the photodiode in the same reverse bias condition in significantly increased to above few µ
- The ratio of photocurrent to dark current is significantly very large as compared to forward bias condition.
- Therefore, photodiode is always operated in reverse bias condition.