# Get transfer function from bode plot

## Homework Statement

What is the transfer function described by this bode plot:
http://img96.imageshack.us/img96/4775/capturegib.jpg [Broken]
*The answer is 3s, but I don't know where it comes from.

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## The Attempt at a Solution

Correct me if I am wrong. A bode plot is a combination of 2 plots, one is dB vs. w, the other one is angle vs. w. Each linear transfer function can be breakdown into 7 types of component to be represented on a bode plot. The answer to this problem is "3s", suggesting that it is the differentiator type. For differentiator with w=3, its bode plot has a slop of 20dB/dcd and intercept at w=3 (dB vs. w graph), and an angle of constant 90 degree (angle vs. w graph). I don't see any of the characteristics on the given diagram. I can see that the two plot has been combined into one, but how exact do I interpret such diagram and be able to come up with 3s as the transfer function? Thank you so much!

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