Question
The current in the forward bias is known to be more (~mA) than the current in the reverse bias (~ A). What is the reason, then, to operate the photodiode in reverse bias?
Solution
The photodiode works in reverse biased condition although the current produced is less. In reverse bias, the width of depletion layer increases thereby reducing the capacitance across the junction. Hence, the response time for absorption of photons increases. Thus, the sensitivity of the photo-diode is increased which is certainly desired.
