Discontinuous graph in time domain simulation SOLVED

I've found that there is a discontinuous graph for V(B) in time domain simulation in the following circuit.

There is no problem when exporting the data in CSV format.

Could you let me know if there is any problem in my circuit?

by drahn90
September 14, 2020

1 Answer

Answer by mrobbins

I'm seeing small, short-lived voltage spikes that happen on the edges of V(B).

This is real, not a simulation error. It happens because MOSFETs have capacitance. (You've chosen MOFSETs with particularly large capacitance, too.)

I do see the spikes in the CSV export as well when I find t = 1e-5 in the CSV, so it's not a discrepancy between CSV and graph.

If I take your circuit and modify it to remove capacitance from the MOSFETs, I remove the spikes:

As to why the plotter draws the transition discontinuously (rather than with a vertical line), my hunch is that this happens when you have too many datapoints and the plotting engine starts plotting them as points rather than as line segments. If you make the time step bigger, for example 10n, then you'll see all the line segments.

ACCEPTED +2 votes
by mrobbins
September 14, 2020

Thank you for your detailed answer.

by drahn90
September 16, 2020

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