# Homework Help: How to find W/L?

1. Jan 23, 2013

### jean28

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. Jan 24, 2013

### jean28

Re: How to find W/L??

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

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3. Jan 24, 2013

### jean28

Re: How to find W/L??

Last one.

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