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Why does this diagram on CMOS switching show the ground voltage rising? (programming.dev)
submitted 11 months ago by to c/askelectronics@discuss.tchncs.de
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This is from a section on why decoupling capacitors should be attached to CMOS chips. It shows current spikes during transitions. Which then because of the inductance of traces connecting power to the chip, will cause the power rail voltage to droop.

But why is the ground voltage also shown to rise? What does it even mean for ground voltage to rise when ground is what voltage is measured against?

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[–] 3 points 11 months ago

If you're measuring ground at the supply, you'll have a voltage drop on both the supply line and the return line. It's much less on a PCB, but if you are switching fast enough with large big voltages, even the inductive load of vias to ground can ruin your day.

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