Why do we use ceramic capacitors alongwith crystal oscillator for 8051 ? why not polar or electrolyt

Why do we use ceramic capacitors alongwith crystal oscillator for 8051 ?
why not polar or electrolytic ?

i think since these capacitorsare used as filters
and their value being in the order peco farade
only ceramic capacitors are available in this range

ceramic caps with crystal act as loading capacitor for oscillator. Usually they are used for adjusting the crystal frequency. Crystal oscillator vendors specify the value of loading caps to be used along with oscillator to give the perfect frequency.

if you check a crystal alone on an oscilloscope you will find that frequency is little higher than that of what is specified, so loading caps shift this frequency to a lower value normally the required value.

Sometimes one of these loading cap is replaced by a trim cap to adjust crystal frequency in realtime.

as replyanandrv said, the values of caps being in pico farads they are made of ceramic. I have no answer for that maybe you can try google?

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