I will start this with a basic overview of our problem.
We designed a baseband amplification board to amplify a baseband signal through two OP37 SOIC-8 stages. The original design specs were that we would only be dealing with positive voltage inputs. However; we just received the information that we now have a negative voltage input and it is too late to redesign the boards.
So we need to figure out how to reverse the polarity of one of our amplification stages but we did not build in the capability to switch the polarity of our gain. Also this is a 4 layer board so none of the traces are accessible.
We are hoping that there may be some devices made with reverse inputs ex: OP37 - Pin 2=(in-) & Pin 3 =(in+) so then OP37(switched) Pin 2 =(in+) & Pin 3 =(in-) which would solve our problem nicely.
Alternatively; are there OPAMPs with an internal gain manufactured? If so, an OPAMP with an internal gain of -1 would also solve our problem nicely.
Any further suggestions on how to solve this are greatly appreciated as well as any information concerning the above two ideas.
It is the second gain stage in the following image.