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Why does this diagram on CMOS switching show the ground voltage rising? (infosec.pub)
submitted 5 days ago* (last edited 5 days ago) by iliketurtiles@programming.dev 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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[–] MangoPenguin@lemmy.blahaj.zone 5 points 4 days ago

Because of voltage drop, if you have a length of wire and run current through it, there is a drop in voltage, so the voltage is higher on one side and lower on the other.

So your voltage on the gnd pin of the IC relative to the other end where its connected to your supply will have a voltage difference that increases with current.