Omega is equal to 1 / RC !

Discussion in 'General Electronics Chat' started by kaznov, Apr 11, 2012.

  1. kaznov

    Thread Starter Member

    Mar 10, 2012
    30
    0
    Hi guys

    can someone please explain to me why omega equal to 1 / RC in a RC circuit because I found some info but still not fully understand it

    Thanks alot
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,157
    1,796
    In an RC circuit that is the so called "corner frequency" where the magnitude of the "ideal" response begins to roll off. It is also the point where the magnitude of the response is 3 dB down.
     
  3. daviddeakin

    Active Member

    Aug 6, 2009
    207
    27
    The 'gain' or tranfer characteristic for an RC filter is:

    A(jw) = 1 / (1+jwRC)

    To get only the magnitude of the voltage you need to square the real and imaginary parts, then take the square root:

    Av = 1 / √(1+(wRC)^2)

    When w=1/RC then you have:

    Av = 1/√(1+1) = 1/√2

    This is the point where the *power* gain is halved, and that is called the cut-off frequency.
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,157
    1,796
    And a *power* gain of one-half says EXACTLY the same thing as:

    1. The power gain is "3 dB down" or
    2. The power gain is "minus 3 dB"
    because
    Code ( (Unknown Language)):
    1.  
    2. 10 * log (1/2)
    3. 10 * (-0.301019996...)
    4. -3.01....
    5.  
     
  5. kaznov

    Thread Starter Member

    Mar 10, 2012
    30
    0
    Thanks alot guys :)
     
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