sine-wave oscillators

Discussion in 'Homework Help' started by zdzislavv, Sep 14, 2009.

  1. zdzislavv

    Thread Starter Member

    Jun 5, 2009

    I've got some questions which I need to answer. My answers are given below. Can you tell me whether they are proper answers and suggest any tutorials / websites where I can find more information about this topic?

    2. What will happen if for the working oscillator with 3-stage CR phase shifter the shifter is replaced with the 4-stage one (explain why) - the same question for RC, LR or RC phase shifters).
    Oscillator will still work, however in different (higher) frequencies. It happens due to phase shift of signal. Both gives 180 + 2pi*r (r=0,1,2,...), for 3 stage shift is 60 degrees, while by 4 stage 45 degrees. We also should mention that if phase shift decreases, frequency increases.

    4. Can a 2-stage (3 stage, 4 stage) CR (Rc, RL, CR) phase shifter be used to make oscillator with inverting (noninverting) amplifier (explain why).
    2-stage normally won't work (in every case because of wrong phase-shift). Higher stages -> by changing the amplifier, output (from amplifier) wave will have different phase, and it will mismatch the condition of oscillation (cond. of phase).

    Source of above questions:


    The other thing which I need to do is to solve the following exercise: Can you give me any suggestions?

    I guess I need to read two values from those two graphs, e.g. |B(jphi)\=1/2 for f=3kHz and phiB=1/(2pi) for the same frequency.

    Then I need to put these values to some formulas. I know two conditions: condition of gain |KB|=1 and condition of phase phi_k + phi+B = 0 or 2k*pi. How to use these formulas for the above values?