Dear all ,
Thanks to electrician . your answer is really helpful . this is another calculation for RC circuit . Please kindly tell me whether it is correct or not .

 

Here is next Opamp.

 

Sallen Key Circuit

 

from above sallen key circuit eq:

 

Hi jjohn,

What is your question? How may we help?

 

Butterworth , Chebychev Response from above sallen-key circuit.
Dear All,
At the top first diagram , I do calculation for frequecy and get f=1/3pi*RC or f=1/2*pi*RC. where actually R =R2+R3 , I tag like R=R1+R2.

Now the last diagram show answer when it is connected to op amp with feedback , freq f = 1/2*pi (sqrt(3(R2 +R3))

I am not sure why square root comes out . I have not calculated for that yet .

Question 1 : Can you say it change freq because of op amp with feedback like sallen-key equation calculation.?

Question 2: Butterworth , Chebychev transfer function come out as in diagram . Butterworth B2(s) = s^2 + s*Sqrt(2) + 1
Chebychev Trasfer function = H/(1.4125*s^2 +0.9109*s +1 )
Can anybody tell where they come from ,and how ?