cut off frequency

Discussion in 'Homework Help' started by jstrike21, Feb 18, 2010.

  1. jstrike21

    Thread Starter Member

    Sep 24, 2009
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    I have a circuit with the transfer function: Vo/Vi=-R2/R1

    How do I get the 3dB frequency from this?
    Is it where 20log(Vo/Vi)=1/sqrt(2) ?
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
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    The transfer coefficient for the relationship you give is constant for all frequencies - there is is effectively no cut-off frequency.
     
  3. jstrike21

    Thread Starter Member

    Sep 24, 2009
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    That is what I thought but I looked at the question again and it gave me GB=2MHz
    so I did 2pi(MHz)=(R2/R1)w
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Can you provide a schematic so that we may see what it looks like?

    hgmjr
     
  5. jstrike21

    Thread Starter Member

    Sep 24, 2009
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    forgot to say its an op amp circuit
    [​IMG]
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    The limiting factor is the slew rate of the op amp.
     
  7. steveb

    Senior Member

    Jul 3, 2008
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    Slew rate can limit the response for large signals. But, for small signals it is the gain bandwidth which limits the response.

    The key thing which is apparent here is that insufficient information has been given so far. We need to know more about the properties of the opamp and whether the analysis is for large signals or a small signal approximation.

    I would guess that the problem has given a gain bandwidth, or an open loop gain with a pole location, and is asking about small signal gain.
     
  8. jstrike21

    Thread Starter Member

    Sep 24, 2009
    104
    0
    GB was givin and it is 2MHz
    I was in class when i was posting earlier and some things were cleared up about this question so i might know how to solve it
     
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