Bode plot confusion

Discussion in 'General Electronics Chat' started by acelectr, May 13, 2011.

  1. acelectr

    Thread Starter Member

    Aug 28, 2010
    73
    0
    Hi, I've attached this bode plot that I did not understand. this plot come from the equation =>
    32x{[20log(f/10)-10log(1+(f/10)^2)]+[20log(f/100)-10log(1+(f/100)^2)]} as it is seen in the plot at 0 frequency we get 0 but actually log0 does not exists. Plus as f goes infinite I would've expect the plot to go to zero and thus not to obtain 32dB instead, as f increases. What is it that I am missing here?:confused:
     
  2. steveb

    Senior Member

    Jul 3, 2008
    2,433
    469

    Can you tell us where this equation derives from. It looks like the formula should be ...

    32 + 20log(f/10)-10log(1+(f/10)^2)+20log(f/100)-10log(1+(f/100)^2)

    ... but, can't be sure without knowing the source.

    That plot is not showing zero frequency at all. Typically, Bode plots don't go down to zero frequency. Although, sometimes people will quote the zero frequency limit, provided it doesn't go to negative infinity (which implies zero on a linear scale).
     
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  3. acelectr

    Thread Starter Member

    Aug 28, 2010
    73
    0
    ok now I've got it. Now thinkink it should've been 32+... finally it makes sense:)
     
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