Do Analog Multiplexers need a GND connection

[Arznei]

Hello,

I am having a hard time getting this straight in my head. I am trying to have an analog test signal pass through an unknown impedance that could have a voltage source inside it. So my plan was to have the impedance decoupled with capacitors like shown in the attached schematic. First of all: I am not even sure this works, so if you can give me some input on that I would appreciate it.

Now on top of that i would like to switch between different outputs, for example the external impedance under test and a known calibration one. I figured it would be best to have the path selection after C1. However I am not sure if an analog multiplexer like ADG739 would work in that instance? I mean the output behind C1 is not really tied to GND, so will it pass through an analog switch without problems?

Thank you for any advice!

[MasterT]

Something is not right with your schematic,
https://www.eecs.tufts.edu/~dsculley/tutorial/opamps/opamps5.html


MUX better to put at the OPA output, than you always would know DC bias point, and control it if it's necessary.