The below is the circuit in question using LTSpice XVII(x64) (

enter image description here

The two sources have the exact same sine wave, just with different DC offsets. One with a DC offset of 5V, the other with 0V.

So, when you subtract, or measure the voltage between Vcc and Vref, you should get a perfect DC value. And we do. But, when you measure the voltage between Vdiv and Vref, it has some AC signal.

I'm going to assume there is a setting or a way LTspice functions that I don't know about.

Here is the output measuring the voltage between Vcc and Vref. A perfect 5V DC enter image description here

Here is the output measuring the voltage between Vdiv and Vref. enter image description here


1 Answer 1


Unfortunately, this is a known problem that's been haunting LTspice XVII since a year or so. It gets even worse, just try making R1 to be 1, then plot the same differential voltage. Adding .opt plotwinsize=0 makes no difference.

The solutions are:

  • impose a small timestep, but it can get very small and the effects seem to be linearly decreasing
  • add .opt method=gear for LTspice XVII from 2020 and beyond
  • use the version of LTspice XVII from May 6 2019 or before (as it appears in the Help > About)
  • use the discontinued LTspice IV.

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