Thank-you @hurz for helping. ☺
RC phase shift oscillator
Theoretically, The gain of Feedback circuit is 1/29.
So I adjusted the gain of Amplifier to 29 for sustained oscillations. Rf=29*R1
But I increased the gain a bit to 44.7 by
Rf=29Kohm
R1=649ohm
To get frequency of 1Khz
F=1/(2×π×R×C×√6)
Assuming C=0.1uF
R=649ohm
