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Homework Help: Circuits and low pass filters

  1. Oct 13, 2004 #1
    You are given a low pass filter of 50nF and a resistor of 100 KOhm.
    a) Draw the circuit diagram;
    b) Calculate the 3dB frequency;
    c) Calculate the impedance of the series circuit of R and C and draw it in the complex plane at
    about 2 decades around the 3dB point and at the 3dB point.
    d) Draw the circuit diagram for a high pass filter with same components.

    I am asked to calculate the 3db freq, right? is this the right formula f = 1 / (2piRC) ?
    and afterwards calc the impedance z = R + jXc where Xc = 1 / (2pifC) ?
    and then getting the decades, say our freq was 31.8Hz , 2 decades below would b 0.318? 2 decades above would b 3180?
    then we should use those values of f to determine the Xc at those frequencies, and then find z at each of these frequencies?
    then we plot a graph showing all the z's?

    pls smne help me coz i'm totally confused!!!
    thanks in advance! :smile:
  2. jcsd
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