I need to put 2 capacitors for decoupling in parallel with the power (5V).

In some guide of my project I did found schema "A", in other schema "B".

Are both equivalent and in parallel? Or only the schema A is parallel and B is in serie? (In Eagle board, but not in schema, I did omit GND for simplicity)

Thank you very much

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In an ideal world they are equivalent. C1 and C2 are parallel in A and in B

A however has its 0.1 µF capacitor physically closer to whatever you are trying to power, so from a decoupling perspective. A is ever so slightly better, judging by the PCB layout.

If possible, put the 0.1 µF capacitor as close to whatever you are trying to power. Literally 1-5 mm away from the pins of your IC.

If you want to make it correct, then you should not use ground wires as you've done in both A and B. You got an entire layer of copper clad. Make use of it.

You will pay the same money for removing 10% copper of the board, or 90% of the board. But if you remove 90% of the copper then that means you probably got thin wires, this is worse and you're doing it with zero gain. Make your traces as wide as you can. Especially regarding your ground.

  • 1
    \$\begingroup\$ Thank you. In every PCB that I send to Fab, I use Top and Bottom layer with poligon GND... This was only an example to understand... Thank you very much! \$\endgroup\$ – sineverba Dec 17 '17 at 16:16

Since the point of the small ceramic cap is to handle the high frequencies, it should be physically close to whatever it is supposed to be across. The larger and slower electrolytic cap can be further away.

In this particular instance, a single ceramic 10 µF cap is all you need. Ceramics are easily available with 10 µF at 5 V. I'd use a 10 µF 10 V cap. You should be able to find those in 0805 package. There is no need for a electrolytic cap here at all, assuming 10 µF is really enough for whatever it is you are trying to do.

  • \$\begingroup\$ I know that they Need to be close as possible to the IC or whatever Need to be... But.... Are they both equivalent and in parallel? Thank you! \$\endgroup\$ – sineverba Dec 17 '17 at 16:02

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