# Reverse biased photodiode gain resistor selection

I have a reverse biased photodiode as shown below.

where R1 = 100kΩ. The output is quite low around 50mV. I would like to replace R1 with 1MΩ to get 10x the output. My concern is, if it will have any disadvantage? Does it have any effect on the rise time?

• It'll affect the fall time. – Brian Drummond Feb 3 '16 at 16:51
• Could you explain a bit? – zud Feb 3 '16 at 17:05
• Could you add an opamp to the circuit? – Voltage Spike Feb 3 '16 at 17:41

$$\bar{v_n^2} = 4 k_B T R$$