Confusing about colppits oscilator

hello my friends
please download the attachment and see the 15 page
Lec_19_Colpitts_Osc_10.pdf

i see every where that oscillation frequency:
../imgqa/eboard/Antenna/rf-ykvp5z0ndvd.gif

what is diffrence?

Sorry, but I doubt that you "see everywhere" for the Colpitt type the formula as given with your 2nd link.
Instead, the formula as given in the pdf doc is correct.

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formula in your 2nd link is used for negative feedback. which is basic requirement for oscillation.(for constant gain)

could you tell more about uday mehta? how it is possible that we have oscillation with negative feedback?

They are the same, provided that C is the series of C1 with C2 (C=C1*C2/(C1+C2) and of course Wx=2*pi*f0.

Z

sorry
I had a mistake.
both answers are correct.
in your pdf W is given. and w=2*pi*f
in your second link c=(1/c1+1/c2)