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For reference, the datasheet I am referring to in this post is given by this.

I was wondering whether anyone could clarify the point of connecting the inverting channel of the succeeding stages of the MEMS microphone assembly pictured to the ground of the actual microphone... is this absolutely necessary? My understanding is that the non-inverting output here is just some voltage [GND,Vdd] which I can interpret as the microphone amplitude.

The succeeding stages obviously share the same ground- I am asking specifically about the resistor Rout and its use.

What is the purpose of Rout? The datasheet does not specify any sort of internal gain setting or anything of the sort, and if you assume an ideal ground then surely nothing precludes doing your own way with the inverting channel of the succeeding stages without bothering at all with Rout?

I can only see Rout as some sort of feedback resistor but I have very little experience with op-amps and MEMS microphones in general- this is my first project dealing with the sort- so forgive me for being a bit clueless as to what its point is...

Example typical single-ended application of a Knowles MEMS (general- many DS's specify this.)

Callous Derpallous
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    It's likely (although not very clear in the linked data sheet) to be about ensuring interconnections between source and receive amplifier are balanced thus more noise/interference resistant: https://electronics.stackexchange.com/questions/591838/is-a-buffered-signal-less-prone-to-interference/591840#591840 – Andy aka Dec 28 '22 at 23:07

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It's likely that the amp drawn on the right of your drawing is oversimplified. There may be feedback paths internal to the part for purposes of setting the gain. In any case, it's good practice to ensure that an amplifier's (antisymmetrical) inputs are presented with similar impedances, both to match impedances of internal feedback and to minimize the voltage offset caused by input bias currents.

In this example, I don't see a practical reason you wouldn't use the symmetrical mic outputs, so I assume it's an example of what you would do if you didn't. Using one of a pair of differential outputs is generally fine, but you'll occasionally find an amp that has a high degree of common mode noise, which the differential connection would eliminate. What they seem to be showing here is that by using ground as the negative input, a single-ended signal can be used as easily. However, you still need ground as a reference, and the RC network shown ensures that the ground does not disrupt the differential input in the same way it could with a direct connection.

Cristobol Polychronopolis
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