How to find Fc (cutoff frequency) of 2nd order PASSIVE LPF?

[sinoo_jahagirdar]

Please help me out in finding fc...We are designing a 2nd order butterworth low pass filter (PASSIVE) using R=1000 and C=33 nF.. Do we need to get the transfer function??..Vin 1-3 v..the circuit dgm is as below:::

-----R1-----------R2------------------
. .
. .
Vi C1 C2 Vo
. .
. .
------------------------------------------

(picture didnt turn out correct, but the capacitor is parallel to the right of the resistors.) :C1 parallel to right side of R1 , C2 is parallel to right side of R2..

R1=100
R2= 1000
C1=C2= 33nF

Please help me out n write me in detail abt this ckt (order of ckt )

 

[FvM]

You can't design a passive butterworth filter without utilizing inductors. Passive RC filters have real poles only, but >= 2nd
order butterworth needs complex poles.

 

[sinoo_jahagirdar]

Re: How to find Fc (cutoff frequency) of 2nd order PASSIVE L

Thanks for reply sir...But the cicuit which i have drawn is RC LPF circuit na??..pls let me describe about this attached circuit....

 

[FvM]

Re: How to find Fc (cutoff frequency) of 2nd order PASSIVE L

It's obviously a kind of Low-pass, but can't have Butterworth characteristic. The transfer function of the filter can be derived by basic
network calculation or found in literature, if you need it (you should know, if). A -3 dB or - 6dB (depends on your definition) cut-off frequency
can be calculated as well.