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
    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.)


    thanks... >.<
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
    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

    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.

  4. n9xv

    Senior Member

    Jan 18, 2005
    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
    thanks!!!! i got it~~~