The current in forward bias is known to be more () than the current in reverse bias (). What is the reason, then, to operate the photodiode in reverse bias?
Solution
Illumination changes the current by generating extra electron-hole pairs.
In reverse bias the dark current is a tiny minority-carrier current, so the light-generated carriers cause a large fractional change that is readily measured.
In forward bias the current is already large (), so the same illumination gives only a negligible fractional change.
In reverse bias the dark current is a tiny minority-carrier current, so the light-generated carriers cause a large fractional change that is readily measured.
In forward bias the current is already large (), so the same illumination gives only a negligible fractional change.
CBSE Class 12 Board · 2012 · Subjective