phase shift oscillator with Circuit

Discussion in 'General Electronics Chat' started by yagnesh, Mar 30, 2009.

  1. yagnesh

    Thread Starter New Member

    Mar 24, 2009
    Hello Sir
    I am Sending you my Circuit daigram and aquaired data. In my circuit,for lower value of Rf and Rin its need High Gain and when i increased Rf and Rin, its need lower gain. why this happened?
    Second, why my freq. is change with change in Rf and Rin?
    and why i did not got that freq which is explain in theory?

    this is my afford, plz help me how can I solve this Quary?

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  2. The Electrician

    AAC Fanatic!

    Oct 9, 2007
    For your unbuffered version of the circuit, you have a theoretical frequency of oscillation of .065/RC; this is incorrect. The theoretical frequency for this circuit is SQRT(6)/(2*pi*R*C). The theoretical required gain for the unbuffered version is 29, but your circuit has a load on the last stage equal to Rin. This changes the theoretical gain and oscillation frequency. You will have to analyze the circuit for each different value of Rin.

    Your buffered circuit has a theoretical required gain of 8, not 29, and the oscillation frequency is SQRT(3)/(2*pi*R*C), provided the last stage is not loaded. The circuit you have shown is loaded at the last stage, and this will change the theoretical required gain and oscillation frequency.