Are the caps necessary?

Hi,
In just about every DIY-Arduino schematic I've seen, there's a capacitor for each of the crystal's legs.
However, some don't have them.
Are these necessary?
If so, why?
Thanks!

PocketHarambe101:
Hi,
In just about every DIY-Arduino schematic I've seen, there's a capacitor for each of the crystal's legs.
However, some don't have them.
Are these necessary?
If so, why?
Thanks!

I think that the specified ceramic resonator already has them built into the chip. So not actually an external component, even though they appear as such on the schematic.

BTW. On my UNO clones which have a 16 MHz quartz crystal instead of the ceramic resonator, I can see those two capacitors are installed.

The Uno, like many, have a crystal, which require 2 capacitors, to create, I believe, a resonant circuit. The crystal, itself, is a very tiny piece of quartz crystal.

You will also see ceramic resonators. These have a ceramic element and the 2 capacitors all mounted in a 3 pin package. Generally, they are no as good as crystals.

Fof

The capacitors are needed to ensure the crystal is on frequency and that it starts reliably.

Those circuits without a capacitor on the crystal are designed by idiots.