On Thu, Mar 30, 2017 at 9:13 PM, Noel Chiappa via cctalk <cctalk@classiccmp.org> wrote: > I'm still not clear, from the discussion, how exactly that nice 'square-wave' > interference is happening - could it be capacitative crosstalk? (I'd have > thought capacitative cross-talk would be inverted - driving a positive voltage > on one 'side' of the 'capacitor' would, I would think, induce an oppposing > voltage on the other. But I'm clearly no EE! :-)
The fundamental rule is 'You can't change the voltage across a capacitor instantly'. There is a related one 'You can't change the current through an inductor instantly'. It (of course) doesn't matter if said capacitor or inductor is an actual component or 'strays'. So instantaneously, a capacitor acts like a constant voltage drop. If the charge on the capacitor doesn't change much (fast signals, high resistors so not much current flow), the 2 sides of the capacitor will be much the same signal (possibly with a constant voltage offset). -tony
