[Microelectronic Circuits 6th Ed.] P2.27 (Regular Ed.) / P2.23 (International Ed.)

Discussion in 'Homework Help' started by Starhowl, Dec 14, 2013.

  1. Starhowl

    Thread Starter New Member

    Dec 3, 2013
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    Can someone please explain to me what I did wrong in trying to solve this task? Or maybe I did everything right and there's an error in both the international and regular edition?
     
  2. Starhowl

    Thread Starter New Member

    Dec 3, 2013
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  3. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I haven't worked through your algebra, but algebra involving moduli is more tricky than ordinary algebra.

    One equation becomes two or three as you have to consider three situations separately

    Say you have to do some algebra with a modulus such as |x| then you must consider

    x>0 then |x| = x
    x<0 then |x| = -x
    x=0 then |x| = 0

    and put these separately into your equation and work it through three times.

    Here is an example that actually a full professor of maths got wrong on another website!

    post#6 there is correct.

    http://www.scienceforums.net/topic/80488-finding-a-absolute-value-quadratic-math-team/
     
  4. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    That does not seem right.

    x>0, then |x|=x
    x<0, then |-x|=x
    x=0, then |0|=0
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Why not?

    x<0, then |-x|=x

    This is clearly wrong. if x = -15 what is |x|?

    Did you read the worked example?
     
    Last edited: Dec 14, 2013
  6. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Some of the links don't open for me. In any event I make the minimum open loop gain to be Aol=20,098. Does that tally?

    Note:
    The value was based on the assumption that the ratio R2/R1 was selected to produce a gain of exactly -100 at the aforementioned amplifier open loop gain of 20,098. The gain falls to -99.5 when the amplifier open loop gain falls to 10,049. If the ratio of R2/R1 is preset to a nominal value of 100 then the answer would be different & easier to deduce.
     
    Last edited: Dec 15, 2013
  7. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Absolute value of negative fifteen is fifteen. In equation form I would write it the following way:
    |-15|=15
     
  8. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Well yes, if the x is -15 then the modulus is +15.

    So how can the modulus equal x, which is -15.

    Think about it.

    If x is always negative and the modulus is always positive how can one ever equal the other?
     
  9. tbinder3

    Member

    Jun 30, 2013
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    whoops.. error
     
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