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Homework Help: Trying to block frequencies

  1. Feb 24, 2014 #1
    1. The problem statement, all variables and given/known data

    (a) The input capacitor and the voltage divider network form another high pass filter. Calculate f3dB for the input high pass filter made with C = 4.7uF and the appropriate R value.

    (b) calculate the f3dB for the output pass filter made with C = 4.7uF and R = 100K


    2. Relevant equations

    f = 1/2*pi*R*C

    2^N=high frequency/low frequency

    3. The attempt at a solution

    Question (a)
    First attempt:

    R1 = 10k
    R2 = 4.7k

    R(total) = (10k)(4.7k)/(10K)+(4.7k)
    R(total) = 3.20k

    Hence the frequency is:

    f = 1/ 2*pi*(3.20k)*(4.7uF)
    f= 1/0.094499
    f= 10.582Hz

    Second attempt:

    R1 = 4.7k

    R(total) = 4.7k

    Hence the frequency is:

    f = 1/ 2*pi*(4.7k)*(4.7uF)
    f= 1/0.1388
    f= 7.205Hz

    Question (b)

    f = 1/ 2*pi*(100k)*(4.7uF)
    f= 1/2.953
    f= 0.3386Hz

    Are any of the frequency values that were calculated correct?

    Thank you
  2. jcsd
  3. Feb 24, 2014 #2


    User Avatar

    Staff: Mentor

    Looks okay to me, but I don't understand what you are doing in your "second attempt" at part a).
  4. Feb 24, 2014 #3
    Thank you for your response. So since the second response doesn't look right then, I will use only the first responses as my answer.

    Thank you very much
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