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How to find W/L?

  1. Jan 23, 2013 #1
    How to find W/L??

    1. The problem statement, all variables and given/known data
    The exercise already tells me that the value of W/L is 2. However, I can't seem to understand where that result came from. I'd like to know how I can get to that conclusion.

    Here is the exercise with the graph of the inverter:
    Inverter image:
    http://i1226.photobucket.com/albums/ee410/jean28x/image2_zps9e7f8724.png

    Exercise, part 1:
    http://i1226.photobucket.com/albums/ee410/jean28x/image_zps136b69f7.png

    Exercise, part 2:
    http://i1226.photobucket.com/albums/ee410/jean28x/image_1_zps32b9a8ee.png


    2. Relevant equations
    Here is a picture of relevant formulas of MOSFETS:
    http://i1226.photobucket.com/albums/ee410/jean28x/image_2_zpse3d8245e.png

    There is also the formula in the hint that is given in the exercise:
    http://i1226.photobucket.com/albums/ee410/jean28x/image_1_zps32b9a8ee.png


    3. The attempt at a solution

    So, using the formula given in the hint, I substitute the values (I already know the 48 KΩ part):

    48k = 1/((125μ)(W/L)(2.5 - 0.5))

    Solving for W/L, I get:

    12 = 1 / (W/L)

    W/L = 1 / 12 = 0.08333

    However, the answer says that W/L is supposed to be 2. What am I doing wrong here???

    Thanks a lot.


    P.S.

    It might be worth noting that, since this is an exercise working with CMOS circuits, then the relevant state that it should be analyzed in is in Triode and Cutoff modes.
     
  2. jcsd
  3. Jan 24, 2013 #2
    Re: How to find W/L??

    Here I will upload the pictures, just in case the links don't work.
     

    Attached Files:

  4. Jan 24, 2013 #3
    Re: How to find W/L??

    Last one.
     

    Attached Files:

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