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Circuit Analysis with VCCS and VCVS

  • Engineering
  • Thread starter Mootix1313
  • Start date
  • #1

Homework Statement


For the circuit in Figure P1.42, suppose R3 = 2*R2, and R2 = 10 * R1. Find the resistor values so that Gv = Vout/Vin = 1000.

question42-1.jpg


Homework Equations



V = IR

for Voltage Controlled Current Source - i(t) = gm * vx
for Voltage Controlled Voltage Source - v(t) = μ * vx



The Attempt at a Solution



Everytime I try to figure out the resistor values I get R3 = 500. The answer is R3 = 5 k ohms which the book gives us.
 

Answers and Replies

  • #2
lewando
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Unless I'm losing my mind, it looks like Vout = 5V2, which is independant of the value of R3.

How do you come up with your answer?
 
  • #3
Unless I'm losing my mind, it looks like Vout = 5V2, which is independant of the value of R3.

How do you come up with your answer?
I said that
Vin = Iin*R1

V2 = .8*Vin * R2
= .8 (Iin*R1) * R2

Vout = 5*V2
= 5 * (.8 (Iin*R1) * R2)
 
  • #4
CWatters
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I think R3 is only needed to calculate Iout not Vout.

Rest deleted as I made a mistake.
 
  • #5
lewando
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Those look fine. If you combine

V2 = .8*Vin * R2

and

Vout = 5*V2

you can get an expression for Vout/Vin as a function of R2 only.

Using your stated constraint for R3 = 2R2, I also come up with R3 = 500 ohms.
 
  • #6
Those look fine. If you combine

V2 = .8*Vin * R2

and

Vout = 5*V2

you can get an expression for Vout/Vin as a function of R2 only.

Using your stated constraint for R3 = 2R2, I also come up with R3 = 500 ohms.
Is it possible that we are a factor of ten off?
 
  • #7
lewando
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I think it is more likely that your book is off by a factor of 10. Are you sure that R3 = 2*R2? Maybe an additional set of eyes on this problem might build the case against your book.
 
  • #8
I think it is more likely that your book is off by a factor of 10. Are you sure that R3 = 2*R2? Maybe an additional set of eyes on this problem might build the case against your book.
This is the question from the book:

2012-08-26200101.jpg
 
  • #9
As it turns out, the book was off. It was supposed to say .5 k Ω and not 5.
 
  • #10
lewando
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That's great! Thanks for the closure.
 

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