I have not included specific values for the feedback network, as it occurs for all values I have tested. Now here is the issue: this receiver only works beyond a certain distance between the transmitting LED and the photodiode; this distance is dependent on the gain, which is the value of the feedback resistor. If I have it too close to the IR LED then the output just saturates to my supply voltage (+10V). Any ideas on why this this happening? I know that it is not simply the capacitor charging up, as it also occurs without that. My best guess is that when I have the LED too close I am generating too much current, which is trying to pull up the output voltage beyond its maximum limit, thus causing it to rail and affecting it internally. I am having trouble convincing myself of this though, because my transmission is a 50% duty cycle square wave, so during half of the period there is no signal at all, and yet the output continues to hold at a steady +10V. Is such an intense amount of irradiation on the photodiode causing a current to persist through the LOW portions of the signal? This it the first time that I am using a transimpedance amplifier in a serious application, so this may be obvious. Many thanks in advance for any insight or tips.
Edit: Here is a plot showing the resistance values that I have tested. More specifically, it shows my maximum transmitted distance vs. the resistance value (gain). The blue curve is my theory prediction, and the red points are my data.