Making guard rings on PCBs for High-Z Amp Inputs

A C-shaped guard ring is acceptable and is standard practice. It's not really a "ring."

• You do not need a fully closed 360° loop.

• The guard ring's job is to intercept leakage paths, not form a Faraday cage.

• Leave an intentional gap where the signal trace enters the +IN node.

• Do not route the guard under the signal trace or jump layers just to close the loop — that usually does more harm than good.

• Drive the guard at the same potential as +IN (voltage follower output is fine).