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Help with proving a transfer function?

  • Thread starter Chandasouk
  • Start date
  • #1
165
0
http://img195.imageshack.us/i/89020004.jpg/

I cannot get the Z2Z3 to appear in the bottom.

I'm saying Zout = Z2 || Z3 so that gives Z2Z3/Z2+Z3 and Zg = Z1

Then H(s) = Zout/Zg = Z2Z3/Z1Z2+Z1Z3

What am I doing wrong?
 

Answers and Replies

  • #2
28
0
You can attack this problem using voltage division. You can get the equivalent impedence across Vo and then divide it by the total impedence seen by the source, Vg.

So:

The voltage seen by Vo:
Zo = (Z3)(Z2)/(Z3+Z2)

The voltage seen by Vg:
Zi = Zo + Z1

So when you divide Zo/Zi and simplify you get the correct answer. Hope that helps! Let me know if you need further explanation.
 
  • #3
165
0
Can you explain why Zi = Zo + Z1? I always thought voltage division was

Vn = Vtotal(Rn/Rtotal)

Where V is voltage and R is resistance. In our case, we would just replace the R's with Z's for impedances but I'm still not sure how you got Zi = Zo + Z1 from that
 

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