It can be as big as you want it to be. However, if you use a large resistive
load at the TIA output and a small feedback resistor, a series RC circuit may
be needed at the output of the TIA to clamp down the peaking. For details,
please refer to the section “The Effect of Low Feedback Resistor Rfx” on the
ADA4350 datasheet. If you use a large feedback resistor (> 1MOhm), you may
consider using a T-network configuration to maximize your signal bandwidth.
Please see the section “Using the T network to implement large
feedback resistor values” in the ADA4350 datasheet.