HELP: how to determaine the capacitance?

Discussion in 'Homework Help' started by Sumychia, Nov 5, 2005.

  1. Sumychia

    Thread Starter New Member

    Sep 3, 2005
    2
    0
    can someone helps me with this question:

    suggest with explaination the criteria to determine the values of C1, C2 and Cs. (do not need to determine the actual value of C1,C2, and Cs for the circuit.)

    [​IMG]

    thanks... >.<
     
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    C1 and Ri act as potential divider and filter. Similarly for Rl, Ro and C2.
    Cs is used to compensate gain at high frequency.
    Have a look at the tutorials on this site for detailed explanation.
     
  3. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi,

    the value of C1 will depend on what cut-off frequency you desire and also serves as a dc blockade so that the gate bias will not be disturb likewise with the signal source. Ditto with C2.

    moz
     
  4. n9xv

    Senior Member

    Jan 18, 2005
    329
    1
    All the above and;

    As a general rule you can calculate the following;

    C1 = 1 / (6.28 * Ri * Fc)

    C2 = 1 / (6.28 * Ro * Fc)

    Cs is chosen to have .1 * Xc of Rs. That is, if Rs was 10-Kohm then Cs should have a Xc (capacitive reactance) of 1/10th the value of Rs @ Fc (cuttoff frequency). So, 1/10th of 10-Kohm (Rs) would be 1-Kohm. The Xc of Cs is to be 1-Kohm. Now find Cs (shunt capacitance) as;

    Cs = 1 / (6.28 * Fc * Xc) or 1 / (6.28 * Fc * 1000)

    Some "fudging" with the value of C1, Cs & C2 are necessary to find a standard value of C that will "fit".
     
  5. Sumychia

    Thread Starter New Member

    Sep 3, 2005
    2
    0
    thanks!!!! i got it~~~
     
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