How to convert unbalanced input to differential for an opamp filter

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I have the following filter working with an unbalanced source chip (DAC).

Now I have to change to a source chip (DAC) that has differential outputs.

Thus I will build a new filter.

Is there a simple way to convert the filter (maintaining identical design/performances/orders) using differential inputs, instead of unbalanced like now?

Is there any simple formula for the components? (Output should remain RCA unbalanced).

It doesn't matter to use two opamps or add an extra one.

(Components values in the schematic are dummy as I cannot reproduce true ones for copyright reason, but please use these one.)


9UXeq.jpg
 
You could connect V4 to the bottom side of R4 and connect a resistor and a capacitor equal in value to R1 and C2 from the positive input of the first op-amp to ground, if the DAC can handle the load. The first op-amp is then used as a differential to single-ended converter.

Compared to the present circuit you lose a zero, but I'm not sure if you wanted it in the first place.
 
You could connect V4 to the bottom side of R4 and connect a resistor and a capacitor equal in value to R1 and C2 from the positive input of the first op-amp to ground, if the DAC can handle the load. The first op-amp is then used as a differential to single-ended converter.

Compared to the present circuit you lose a zero, but I'm not sure if you wanted it in the first place.

Thanks! That was exactly what I simulated, but I didn't get the same slope...

Any way to maintain all zeros?

What about to duplicate U1 and make U2 single ended converter (fed by two U1)?
 
Replacing C2 and the capacitor from the positive input to ground with RC series networks should do the trick. With R = 10 kohm and C = (34/44)*300 pF, for example. Changing the second stage into the differential-to-single-ended converter seems more complicated to me.
 
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