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Design >> Analog Design >> Unsolvable Prob: Microelectronic circuits by sedrasmith 5th Ed.
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Message started by VINAY RAO on Mar 8^th, 2011, 11:24pm

Title: Unsolvable Prob: Microelectronic circuits by sedrasmith 5th Ed.
Post by VINAY RAO on Mar 8^th, 2011, 11:24pm

Hi,
Pl. Refer to Exercise No.4.31, page no- 306 for which data is referred from the example 4.11. (I attached this page)
Here in this problem Ri, R0, Av0, Ais and Gm will be same and it doesn’t depend on Rsig and RL.
As per problem Exercise 4.31:
1. When Rsig and RL is changed: In this problem, no information about the vi and vo is given. I can find these vi and v0 only for RL = ∞ condition. For RL = ∞, I got vi = 8.18mv and vo= 81.8mv. When RL is connected then how can I find Rin, Gv and Rout?

Thank you.

Title: Re: Unsolvable Prob: Microelectronic circuits by sedrasmith 5th Ed.
Post by loose-electron on Mar 10^th, 2011, 10:57am

Is this a school homework problem?

Title: Re: Unsolvable Prob: Microelectronic circuits by sedrasmith 5th Ed.
Post by VINAY RAO on Mar 11^th, 2011, 5:11am

No it's not a home work problem. It's a matter of my own interest and i am not finding any ways to solve it.

Title: Re: Unsolvable Prob: Microelectronic circuits by sedrasmith 5th Ed.
Post by Alexandar on Mar 11^th, 2011, 5:37am

This forum is not here to solve your homework problems. A hint that i can give you: consider that these parameters should not depend on Vi or Vo. So therefore it does not matter what value they take.

Title: Re: Unsolvable Prob: Microelectronic circuits by sedrasmith 5th Ed.
Post by VINAY RAO on Mar 16^th, 2011, 11:15pm

@Alexander: Thank you for your reply. I repeat here again, the problem which i posted is not a home work problem. Getting to know the procedure to solve these type of problems only helps me to strengthen my basic understandings.

Still my doubts are not cleared yet.

part a) When Rsig changes:
If Rsig changes then surely vi also changes then CURRENTin also changes. Do you feel like, the changes in vi and the current (which is flowing into the two port) is same hence Rin doesn't change or bcz of any other reason?

part b) When RL changes:
When this happens, vo changes hence similarly Av (But Avo is constant) and also vi. As vi changes and also the current (into two port)and hence Rin has to be changed. But the problem here is that, neither i know vo nor vi or the current flowing in to the two port => unknowns are vi,vo,Rin,current (into two port) when load is connected. How can i find Rin with these many unknowns (only known thing is Av which can be calculated from Avo, Ro and RL)?

Note: if i assume Rin to be constant (As you told to keep every parameter constant)then it doesn't match the answers given. In part (b) & (c) of exercise 4.31, Rin also changed by changing RL.