Use of Grounding capacitor for Crystal oscillator.

[nikhildascl]

I did some projects using microcontroller. But still i i don't know what is the use of capacitors that are used with crystal oscillator. Please tell the reason. Thank you in advance

 

[cameo_2007]

Read up Pierce oscillator:
https://en.wikipedia.org/wiki/Pierce_oscillator

and more on google about that.

 

[:pH]

Refer to the attached figure :

The crystal in combination with C1 and C2 forms a pi network band-pass filter, which provides a 180 degree phase shift and a voltage gain from the output to input at approximately the resonant frequency of the crystal. To understand the operation, note that at the frequency of oscillation, the crystal appears inductive. Thus, it can be considered a large, high Q inductor. The combination of the 180 degree phase shift (i.e. inverting gain) from the pi network, and the negative gain from the inverter, results in a positive loop gain (positive feedback), making the bias point set by R1 unstable and leading to oscillation