Electronics > Beginners

Do bypass caps invert the signal? 1010101 to 0101010

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Beamin:
I watched the video on bypass caps and since they re put in series on high speed lines on processors wouldn't it invert the signal? The cpu/mcu puts out a pulse it charges up the cap then the cap discharges on the next pulse sending it along: wouldn't this exactly invert the signal? Not the caps the smooth out power but when you see them around/under a high speed chip. Or do electron not work like this? Data lines are kind of like RF due to the speed.


On a related note is there a limit how fast processors can go? I notice on pcbs they go to great lengths to make the traces the same length and other things but when do these start turning into antennas that are giving off GHz signals, so much that it just won't work outside a silicon die?

Zero999:
How the heck can a bypass capacitor invert the signal?  Post a link to the video. No one knows what you're talking about without having seen the video first!

The only thing I can think of is there's an RC time constant and the signal is being shifted by 180o, but that's not how one would use a bypass capacitor, which should be high pass.

enjoy.cowboy:
Thats not how this works at all. The bypass cap will filter out some frequencies to ground, it doesnt tap off into another data line. All the bypass cap does is cut some of the judder and flutter in the data line/clock line so the noise doesnt add up,when going to another tranny.  Also the DC phase shift wouldnt cause the digital signal to be inverted. If that would be the case, all we would need to build a computer would be enough caps to build nand gates ;) The signal measured at the cap cannot be considered logical, as well

iainwhite:
@ Hero999

I would guess it was one of these videos:
EEVblog # 859 - Bypass Capacitor Tutorial
EEVblog #1085 - Bypass Capacitors Visualised!
EEVblog #1081 - Are Bypass Capacitors REALLY needed?

hamster_nz:
I think you have confused bypass capacitors (between a signal and ground) and coupling capacitors (between the source and sink for a signal).

Coupling capacitors block any DC, but pass the high frequency digital data from the source to the sink. They acts is a high pass filter.

A bypass capacitor allows any high frequency signal (usually noise) to go to ground. You wouldn't usually use them on a digital signal, only on the power.rails.

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