Band stop filter

Discussion in 'General Electronics Chat' started by BOB?, Feb 4, 2008.

  1. BOB?

    Thread Starter New Member

    Feb 4, 2008
    First I want to apologize for my bad English :(
    On the forum I have found some information about the band-stop filter.
    But the formulas are
    C2 = C3 = 0,5(C1)
    Fnotch = 1/ (4*PI*R3*C3)

    My problem is that in my scheme R1 <> R2 and C2<>C3
    Now my question is, does anybody now how I can calculate my Fnotch. :confused:
  2. Papabravo


    Feb 24, 2006
    Well you have a low pass filter in parallel with a high pass filter. You can write an expression for the complex impedance of each filter and then combine the two impedances as (Z1*Z2)/(Z1 + Z2). Take the derivative with respect to frequency and solve for zero. That will give you the frequency where the impedance is a minimum. That is the bottom of the notch.
  3. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    It looks like you have a twin-t notch filter arrangement, however, your schematic doesn't show the proper values for the components of a twin-t notch.