What can I learn from an equivalent circuit model of photodiode like the following?
I've actually gone the whole way beginning from doping semiconductors through each noise term to the amplification gain.
Now I'm at the application stage and I stumbled over this circuit and noticed it is quite common. But since I don't see any technical purpose of it, I guess it is constructed to understand the photodiode itself in a technical way. But what does it tell me really? And why is nearly everything parallel to each other?
I've seen this EE.SE question (equivalent circuit for solar cell) which is quite connected, but doesn't touch it directly. However, it hasn't been answered yet anyways.
To be more precise: I'm more interested in the circuit itself and less in the single parts of it. I probably can google each part of it but what is about the circuit itself?