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Homework Help: Extracting information from a Bode Plot (PM, GM, etc..)

  1. Jun 28, 2015 #1
    Hi all,

    1. The problem statement, all variables and given/known data


    This is the loop gain (A.F.) of unity feedback system.

    I need to extract

    DC Gain
    GBW (is GBW Gain Bandwith ?)
    f unity (I suppose this is unity frequency)
    Phase Margin
    Gain Margin

    What is the optimal PM and f2/GBW for time and frequency domain applications?

    2. Relevant equations
    Don't know => this is not really homework as such, plus in the books I got about electrical engineering not much is said about stability and feedback...

    3. The attempt at a solution

    U guys don't need to solve this for me,

    What I want is instructions how I can solve it, since I truly have no material about this topic, then I shall try and present it, and you guys can help me further

    Kind Regards.
  2. jcsd
  3. Jun 28, 2015 #2
    DC Gain =>

    80 = 20 log | DCGain |

    So DC Gain = 10^4 = 10000

    Is this correct?
  4. Jun 28, 2015 #3

    rude man

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    Homework Helper
    Gold Member

    Next: bandwidth?
  5. Jun 28, 2015 #4


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    Loop gain for a unity feedback system is identical to the open-loop gain of the amplifier.
    Hence, you have nothing to do than to apply the definitions of the various data you are interested in.
    Normally, the "bandwidth" is identical to the 3dB-Bandwidth.
    Stability margins can easily derived by using the appropriate definitions.

    Do you know all the definitions?
  6. Jun 29, 2015 #5


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