Confused about PD TIA Simulation in LTSpice

[marloh]

I'm trying to simulate the feedback network on a Photodiode Transimpedance Amplifier that I am working on and I'm very confused by the results. I'm getting a gain of -40db at low frequency 

This is the procedure that I'm trying to follow: https://www.allaboutcircuits.com/technical-articles/negative-feedback-part-8-analyzing-transimpedance-amplifier-stability/

Please help
I'm trying to simultaneously learn the LTSpice software and the TIA and I can't figure out where I'm going wrong

[aliarifat794]

You have to set up your TIA circuit correctly in LTSpice according to the schematic provided in the article you referenced. This includes the photodiode, feedback resistor, and operational amplifier (Op-Amp) configuration.Before analyzing the AC behavior, it's essential to verify that the DC operating point of your circuit is stable and within acceptable ranges. This involves checking voltages and currents at different nodes in the circuit. Perform an AC analysis to determine the frequency response of your TIA. Plot the magnitude and phase of the gain (trans-impedance) across a range of frequencies.

[AnalogTodd]

Important thing to look at DC bias points as @marloh pointed out. The op amp you are using is not the same as the one in the article referenced, and so there is a question as to how close the inputs can go to the negative rail. Your negative rail is at ground, and your input signal is also at ground (shows no DC offset). The LT6015 is listed as an 'over-the-top' op amp and as such can operate beyond the nominal rails. The OPA140 is listed as rail-to-rail output and does not say the inputs can handle going past nominal rails.