4.90 A reverse-biased photodiode is specified to have a dark current of 100 pA and a responsivity of 0.5 A/W. It is connected to the transresistance amplifier shown in Fig. P4.90. Assume an ideal op amp. (a) What is the reverse-bias voltage across the photodiode? (b) What is the output voltage vO with no illumination? (c) What is the output voltage vO with 10 µW of light incident on the photodiode?