Grounding IC with 100n cap?

apc42069

apc42069

Well-known member
Hey all-

I’ve found a few posts across the World Wide Web talking about grounding the vcc pin of an IC with a 100n capacitor. I’m still learning the basics of circuitry & would love some help understanding this.

For context - I recently built an envelope filter (CDXL reissue), but the effect only works when I’m touching the pins of LM358. I can’t really figure out why, and I know specific guidance on that should prob be posted to Troubleshooting - so feel free to ignore this bit.. but any help understanding the concept of using caps to ground ICs would be V much appreciated.

Thanks!
 
The 100nF caps at an IC’s Vcc pin to ground isn’t grounding the pin (the IC wouldn’t receive power in that case). Remember that capacitors block DC signals but pass AC signals. That cap is a decoupling cap that filters out noise and suppresses transients in the Vcc line to ensure the power to the IC is stable. These work in conjunction with the capacitor network(s) in a circuits power block(s).

Note that these are sometimes called ‘bypass’ caps. They can provide power in the event of (short) power drops—typically the result of switching and/or variable load.

Best practice is to place them as close as possible to the pin. We’re dealing with slow signals here—not super fast digital logic—so there’s more leeway.

Set up a troubleshooting thread for your circuit and provide some pictures.
 
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