I am putting together an analog PCB. I am reading an audio signal and using large gain to clip it (effectively a crude digital signal 0-5V) using a differential amplifier. It is a 2-layer PCB with the bottom layer being my ground plane. The datasheet for the op amp recommends surrounding the input stage resistors with a grounded polygon for shielding. The main trace digital output trace has to run back nearby the input stage unfortunately given design constraints.
My question is: should this shielding polygon (via-stitched) extend to connect to local analog ground pins? Or should my stitched polygon simply "float" and then only use vias to connect nearby ground pins directly to the bottom layer ground plane?
Not shown: bottom layer is solid ground plane. SGNL is the large-amplitude signal. I do not have a power plane, simply routed power traces. My concern is that connecting local ground pins to the polygon will allow a careless ground loop somewhere.