I am trying to calculate the gain-bandwidth product of a project where I am reading photodiode output current measurements. I aim to find an op-amp to buy to use as a transimpedance amplifier. The typical output current for the photodiode is 9 microamps (https://www.vishay.com/docs/81519/bpw21r.pdf), and this being the typical output current, I want this to correspond to 2.5V from a voltage swing of 0V to 5V. The bandwidth required in my application is 113 kHz.
I commonly see that the gain for transimpedance amplifiers are in the form of V/A (e.g. 400 kV/A). Am I right to use the 2.5V/0.9uA for the gain value in the gain-bandwidth product?
If not, how do I convert the gain value to be unitless in this situation?