Thanks for your reply, it is quite helpful. Could I ask for some detail?
1. Why noises at VDD act as common-mode voltage? And what is the common mode voltage in digipot?
2. Do you mean that the noises will influence the wiper resistance slightly, and the resistance will in return influence the output voltage of the TIA? Is it correct to say that the VDD noises will not add noise to the digipot directly but only in an indirect way described above?
3. Sorry as a newbie, I am not very familiar with protection diodes, could you please illustrate a little on this?
Best regards,
Richie