My question is about the ADL5304 Log Amplifier.
I used this Log Amp on a board design and in general it works fine. I am able to get 8 decades of dynamic range (outstanding!). The input to this Log Amp is a photodiode, an EPM705, similar or identical to the one that is used in the Application Section of the ADL5304 data sheet.
However, I observe that with no light on the photodiode, the output of the log amplifer slowly ramps up to about 2 volts. I am very careful to make sure there is absolutely no light on the photodiode.
Is this due to leakage current in the photodiode? I know that the ADL5304 has "Adaptive Bias Current" control, and I exploited that feature in my design.
I have attached the schematic here.