I have (in the example circuit) a photo diode with the following data sheet: http://www.ibsg-st-petersburg.com/datasheet/PD/PD24-01-HS.pdf.
Now I was wondering (after there is no data about it in the data sheet): Why is it important how high the negative voltage bias is (except for determining the dark current)? Where does the negative voltage drop come from, and how do I calculate it?
In the circuit I have the resistor R1 with the resistance 1 kOhm, the diode D1 with a voltage drop of approximately 0.7 V, the diode D2 with resistance of approximately 70 kOhm (according to the data sheet) and R2 with "low resistance". Then I get a voltage drop of approximately 2.9 V over the diode. Is the calculation correct, or did I forget something?