I have this ADC driver circuit:

enter image description here

There is a passive filter downstream of the driver which works as desired. I'm focused here on the active filter. When I run AC analysis on this circuit configured for a differential input I get the desired and identical frequency response at Vout+ and Vout-

enter image description here

However I need single-ended input. I've configured the circuit in LTSpice like this:

enter image description here

Running AC analysis there is a difference in the frequency response between Vout+ and Vout-

enter image description here

How can I modify this circuit to provide the (symmetrical) frequency response I get with differential inputs using a single-ended input?

  • \$\begingroup\$ You should link the data sheet for the differential amplifier. \$\endgroup\$
    – Andy aka
    Dec 17, 2021 at 22:57
  • \$\begingroup\$ The main lowpass is still symmetrical. That higher frequency feature is not related to it. Probably specific to the used amplifier. \$\endgroup\$
    – tobalt
    Dec 18, 2021 at 6:53
  • \$\begingroup\$ You'll probably need to convert your single ended output to a differential one. Something like this. \$\endgroup\$ Dec 20, 2021 at 18:36
  • \$\begingroup\$ @aconcernedcitizen isn't the output already differential? \$\endgroup\$
    – davegravy
    Dec 21, 2021 at 19:20
  • \$\begingroup\$ @davegravy You said you need the filter's input to be driven by a single ended output. So if you intend on keeping the filter's differential output then you need to convert your source's output to be able to drive the filter's differential input. \$\endgroup\$ Dec 22, 2021 at 7:49


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