Figure 7. Characteristic I-V Curves of an OSI Optoelectronics photodiode for Photoconductive and Photovoltaic modes of operation. P0-P2 represent different light levels.
This relationship is shown in figure 7. From equation 7, three various states can be defined:
a) V = 0, In this state, the dark current IP=0.
b) V = +V, In this state the current increases exponentially. This state is also known as forward bias mode.
c) V = -V, When a very large reverse bias is applied to the photodiode, the dark current becomes the reverse saturation current, ISat.
Illuminating the photodiode with optical radiation, shifts the I-V curve by the amount of photocurrent (IP). Thus: