How to attenuate an already amplified output?

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Discussion Overview

The discussion revolves around the challenge of attenuating an already amplified output from a high pass filter (HPF) circuit. Participants explore various methods to achieve an output that matches the input at the frequency where amplification begins, considering both theoretical and practical aspects of circuit design.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests introducing another capacitor in series or using a voltage follower to achieve the desired attenuation.
  • Another participant proposes using an inverting opamp circuit and setting its gain to the inverse of the HPF circuit's gain to accommodate the inversion.
  • A participant expresses confusion about why setting the inverting opamp's gain to the inverse of the HPF's gain would work, noting that it seems to swap the pole and zero, leading to new capacitor values.
  • Another reply clarifies that a simple inverting amplifier stage should not affect the poles or zeros of the total transfer function, suggesting that if the filter's gain is x2, the inverting amplifier's gain should be set to -1/2.

Areas of Agreement / Disagreement

Participants present multiple competing views on how to achieve the desired output. There is no consensus on the best approach, and some participants express uncertainty regarding the implications of their proposed methods.

Contextual Notes

Participants discuss the implications of gain settings and circuit configurations, but there are unresolved questions about the effects on the overall transfer function and the specific values of components needed.

chebyshevF
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I have a high pass filter circuit, which I've designed from a transfer function, and from the Bode Plot, I'm getting some amplification, yet I don't want that. I just want my input=ouput at the frequency where amplification starts. How can i go about to do this?

Should i introduce another capacitor in series? A voltage follower perhaps?
 
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chebyshevF said:
I have a high pass filter circuit, which I've designed from a transfer function, and from the Bode Plot, I'm getting some amplification, yet I don't want that. I just want my input=ouput at the frequency where amplification starts. How can i go about to do this?

Should i introduce another capacitor in series? A voltage follower perhaps?

If you can accommodate the inversion, use an inverting opamp circuit and set the gain to 1/ the gain of the HPF circuit's gain.
 
^^Actually I tried an inverting opamp, yet didn't think of setting the gain to the inverse of my HPF circuit's gain. I don't understand why though? So it swaps the pole and zero that i have, hence i get new capacitor values..i can't quite put my 'finger' on it but it kinda makes sense.
 
chebyshevF said:
^^Actually I tried an inverting opamp, yet didn't think of setting the gain to the inverse of my HPF circuit's gain. I don't understand why though? So it swaps the pole and zero that i have, hence i get new capacitor values..i can't quite put my 'finger' on it but it kinda makes sense.

A simple inverting amp stage after the output of your filter should not affect any poles or zeros of the total transfer function. If the gain of your filter is x2, just make the gain of your inverting amp stage -1/2.
 

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