Help Designing Circuit from Transfer Function

Discussion in 'Homework Help' started by aje35, Aug 1, 2012.

  1. aje35

    Thread Starter New Member

    Aug 1, 2012
    1
    0
    Hello,
    I am an electrical engineering student and taking an advanced circuits class.
    I have been tasked to design a circuit from a given H(s) transfer function. The guidelines I must operate within are using:
    - an op-amp
    - resistors ranging from 100Ω to 10MΩ
    - capacitors ranging from 200pF to 10μF.

    The given transfer functions are:

    H1(s) = (0.1s + 6000)/(s + 1200)
    H2(s) = 60000/(s+500)^2

    Any insight or help in to this problem would be greatly appreciated.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    I found this post in "the completed projects forum", where it will stay "moderated" (invisible to others).
    As it says it is for completed projects and not for questions.
    I moved it over here and made it visible, so others can reply on the post.

    As it looks like homework, what have you done to get a solution?

    Bertus
     
  3. #12

    Expert

    Nov 30, 2010
    16,349
    6,840
    I only looked because I'm completely useless at this and hoped to learn from somebody else's answer.
     
  4. Bill B

    Active Member

    Nov 29, 2009
    61
    0
    Is this for the design of an active filter?
     
  5. #12

    Expert

    Nov 30, 2010
    16,349
    6,840
    The "S" terms would seem to indicate that. Hoping aje35 responds.
     
  6. mlog

    Member

    Feb 11, 2012
    276
    36
    The first one looks like a lag filter, or more appropriately a lag-lead, which means the lag is dominant. The second one looks like a critically damped 2nd order low pass filter.
     
  7. daviddeakin

    Active Member

    Aug 6, 2009
    207
    27
    Find the DC gain of the transfer function (when s\rightarrow0)
    In this case that gives 6000/1200 = 5

    You also have a pole at s = 1200 rad/sec
    And a zero at 6000/0.1 = 60000 rad/sec
    This is a low-pass shelving filter, so you could perhaps use the opamp to provide a gain of 5, and then follow it with this:
    [​IMG]

    Here you have a DC gain of 0.24
    And two poles at 500 rad/sec

    You could perhaps use a filter like this:
    [​IMG]
    which takes care of the DC gain and one pole, then follow it with a passive RC filter to give the second pole.
     
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