HI George,
The frequency response is very bad. The configuration you made by inserting 1kohms between the VNA source and -IN forms an ordinary voltage amplifier with a gain of -10 and not a transimpedance amplifier. Can you do the following for me and let's see if we can get better results.
- Put a 50 ohms termination in R2.
- Change the value of the R1 to 100k. Add Caps connected to the R1 and ground. The value of this caps should be the same with the value of the capacitance on your photodiode.
- Put a 50 ohms series resistorin R9
- Input Source should be +10dBm.
- Get the frequency response and upload it here.
Best regards,
Emman