How to find W/L of this CMOS??

Discussion in 'Homework Help' started by jean28, Jan 24, 2013.

  1. jean28

    Thread Starter Member

    Sep 5, 2012
    76
    0
    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/...ps9e7f8724.png

    Exercise, part 1:
    http://i1226.photobucket.com/albums/...ps136b69f7.png

    Exercise, part 2:
    http://i1226.photobucket.com/albums/...ps32b9a8ee.png


    2. Relevant equations
    Here is a picture of relevant formulas of MOSFETS:
    http://i1226.photobucket.com/albums/...pse3d8245e.png

    There is also the formula in the hint that is given in the exercise:
    http://i1226.photobucket.com/albums/...ps32b9a8ee.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. toffee_pie

    Active Member

    Oct 31, 2009
    162
    7
    them photos dont work
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Post your pictures HERE attached to your reply, not over at PhotoBucket where we cannot open them.
     
  4. jean28

    Thread Starter Member

    Sep 5, 2012
    76
    0
    Here are the pictures.

    First one is the circuit, second and third are the exercise with the answer, and the fourth is a page with possibly useful formulas.
     
  5. toffee_pie

    Active Member

    Oct 31, 2009
    162
    7
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