Cut/Boost of Shelving Filter

Hello everybody

This circuit is a high shelfing-Filter. I do have trouble calculating the maximum cut / boost. I know that the devider (R3 and R4) sets the maximum cut and boost but how do I calculate it exactly, with the given resistor values? Thanks for your help!

max boost=max cut=20log ((1-2R4/(R3+R4))=16.8dB
You will get more attention if you post it to Drawing Board.

Thank you very much for your help! I really appreciate it!

@moapms:

With this equation, I get the max. cut of -16.8dB. I know that the max. Boost is the same, with +16dB. But the equation for the max. boost must be slightly different?! Do you know this equation as well?

Here you go:

Thank you very much!!

blackfield said:

Hello everybody

This circuit is a high shelfing-Filter. I do have trouble calculating the maximum cut / boost. I know that the devider (R3 and R4) sets the maximum cut and boost but how do I calculate it exactly, with the given resistor values? Thanks for your help!

Click to expand...

Note that, according to the mathematical analysis, the max boost/cut will never be achieved because it is an asymptotic response, that can be reached only at a virtual infinite frequency. In reality, the finite gain of the opamps will define the actual response.
I would suggest you simulate the circuit in LTspice (a free software by Linear Technology), so you will see practical results and how components interact with the actual response.