I'm a beginner in EE. Lastly I read a lot about this field and I want to jump in.
I think of a toy PCB design, to experiment essentially. I picked the different hardware so that all the components have digital outputs, which is what I want to stick with (less complex, no type mixing, less costly). As well, the power source is an AC to DC adapter. So no AC in the circuit, apparently.
I get that current is not perfect in the real world. So a capacitor near a Vcc pin of an IC is needed to smooth input current and limit its own impedance.
Given these elements:
- Is it still needed to put a decoupling capacitor to each ground on this DC circuit? Isn't it useful to filter high frequencies (AC) only? Do we really care about the noise a ground may have?
- would an ethernet PHY really need a decoupling capacitor in this circuit? Do they generate so much spikes by themselves?
I keep seeing decoupling capacitors in the schematics I read (Raspberry Pi, Arduino, and others). But their constraints are different, I guess.