The measured transimpedance of the latest POY11 PD matches my model very well up to 100 MHz. But at about ~216MHz I have a resonance that I can't really explain.

The following is a simplified illustration of the resonant circuit:

Perhaps my model misses that resonance because it doesn't include stray capacitances.
While I was tinkering with it, i noticed a couple of things:
- the frequency of that oscillation changes by grasping with finger the last inductor of the circuit (the 55n above); that is adding inductance
- the RF probe of the scope clearly shows me the oscillation only after the 0.1u series capacitor
- adding a small capacitor in parallel to the feedback resistor of the output amplifier increases the frequency of the oscilaltion |