# NCEES sample exam problem - pi-pad attenuators



## schmidty99 (Jan 14, 2010)

I'm working the NCEES Electronics sample exam and I have a problem that is something I've never been exposed to. Its about a "pi-pad" attenuator and I'm supposed to list the y-parameters. I can't find anything referencing a pi-pad attenuator in any of my study materials. Does anyone have any info on how to do this problem or point me in the right direction, websites, etc? I can list the details tonight if someone wants them. Thanks in advance.


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## schmidty99 (Jan 14, 2010)

I don't know why I couldn't find this last night...

http://www.electronics-tutorials.com/basics/attenuators.htm

If anyone has anything to add, please feel free. Thanks!!


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## schmidty99 (Jan 15, 2010)

I guess I spoke too soon. The problem is looking for "y-parameters" and the link I provided doesn't say anything about them. It doesn't seem like too difficult of a concept, but I just can't find anything on the y-parameters. Please help!


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## benbo (Mar 1, 2010)

schmidty99 said:


> I guess I spoke too soon. The problem is looking for "y-parameters" and the link I provided doesn't say anything about them. It doesn't seem like too difficult of a concept, but I just can't find anything on the y-parameters. Please help!


Try starting here -

http://en.wikipedia.org/wiki/Admittance_parameters

Basically you are going to have that pi looking resistive network you have in the other link as a black box. On one side you will have V1 and I1 going in, on the other side V2 and I2 coming out, so you are looking for admittance parameters, as opposed to z-parameters, or impedance parameters. Maybe I can figure it out, but I haven't got a lot of time right now - If you don't come up with something I'll try later. In this case it might just be the reciprocal of those z values in the link you found.

This is one of those problems you can't really plan for. It's a small signal analysis, network parameter problem. A good book for weird probs like this is "The Art of Electronics." That's only because you won't have access to wikipedia.


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## rshankle PE (Mar 1, 2010)

Hi Schmidty99,

I'm guessing you are working one of the practice problems from the book that has the circuit board on the cover

(going from memory here since my copy is not in front of me but the problem sounds familar.)

In the EERM book (8th edition) on page 29-15 it describes the y-parameters. Equation 29.61 shows how they are used in a two-port network to show the

relationship between V1, I1, V2 and I2. Then in figure 29.18 it shows how to compute y11 y12 y21 and y22.

If you need help on this send me e-mail rshankle.at.sparrow-labs.com (replace .at. with @)

take care


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## benbo (Mar 1, 2010)

^^^

If it's in the EERM, then forget what I said and look it up there. I actually don't know where my EERM is.

"The Art of Electronics" is still a good book for oddball problems, if you can find a used copy.


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## schmidty99 (Mar 1, 2010)

Thanks guys! Yup its the NCEES sample exam and solutions, problem 102. You are awesome. I think I even looked that on page 29-15 and I didn't recognize it. I'll try to work it out and give back a holler. Probably won't be until tomorrow. Thanks again!


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## jimbo7825 (Oct 10, 2014)

I hate to bring a topic up from the dead, but I cant seem to find anything on how to solve this question. The solution itself is just arithmetic but the reasoning for what the they did I cant find.


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