Hi,

I'm working on a photodiode circuit design using HMC799. When I calculate and evaluate the noise gain, I couldn't find any information related to the parasitic capacitance of the feedback resistor. As the feedback resistor is integrated inside the chip HMC799, the parasitic capacitance might be extremely small. If so, the circuit's stability becomes an issue. Is there any extra information I can use to calculate the noise gain model?

Thanks.

Hi,

HMC799 is stable for input capacitance of 0pF,1pF,2pF,3pF as it can be seen from the datasheet. As the input capacitance is further increased, dominant pole(first pole) would be shifted to lower frequencies further and the amplifier would become even more stable. There is not a model, but through input referred noise density, an estimation can be done. what is the photodiode you are using and what is its parasitic resistance and capacitance?

Regards

Sinan