how to find inductor value on fr formula?

Discussion in 'Homework Help' started by kee23, Sep 20, 2012.

  1. kee23

    Thread Starter New Member

    Feb 1, 2012
    10
    0
    Hello,

    on the question it says i need to find a resistor and inductor values if i have
    fr= 10.7Mhz Capacitance=0.1nF BW=200kHz
    I was guessing that I can use the frequency resonance formulas and after that, i don't know to simply it to find Inductor value.

    Can someone show me the steps to simplify on the formulas? or am i thinking it wrong?


    Thanks.
     
  2. mlog

    Member

    Feb 11, 2012
    276
    36
    Do you know the equation for resonant frequency? If you knew it, could you use algebra to manipulate the equation and solve it for a variable? Is your filter supposed to be passive; that is without any electronic amplification?
     
  3. kee23

    Thread Starter New Member

    Feb 1, 2012
    10
    0
    it's an active filter, but not much need to worry. and formula should be 1/2pi square root LC that's what i meant, i don't seem to know how to do it

    answer for inductor is 2.27uH
     
    Last edited: Sep 20, 2012
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
     f_r=\frac{1}{2\pi \sqrt{LC}}

     {f_r}^2=\frac{1}{4\pi^2 LC}

    Now make L the subject of the equation.

    Presumably this is a series LC circuit - otherwise you must apply the parallel case equation - which in your case would require the concurrent solution for the R value as part of the exercise.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744

    2.2uH
    Calculator for resonance
    http://www.1728.org/resfreq.htm
     
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