Do I need more capacitance for my crystal?
Some years ago I was accosted out in the engineering lab, and dragged over to stare at a scope.
The question was &quot;Why is this Xtal oscillator amplitude larger than the simulation predicts?&quot;
Given a number of issues and assumptions, and simulation nonlinearity behaviors, I was puzzled why a &quot;precise amplitude&quot; was expected.
However after a day or so, I realized the LOSSES within the ESD structures were not being simulated (and indeed likely were a bother for anyone to accurately measure, because the ESD clamping behavior is quite nonlinear and often very slewrate dependent), yet the ESD losses (at both ends of that PI matching/inverting 2_capacitor 1_Crystal circuit) might require MORE output power from the amplifier to overcome ESD losses.
And more output power requires LARGER voltage swings.
And larger voltage swings will trigger the ESD clamping behaviors.
Why is your waveform not moving below Ground?