state-variable and biquad filters

Jony130

Joined Feb 17, 2009
5,488
OK I see why you get confuse.
We set each integrators to have Fc = Fo = 7.23KHz and this Fc is -3dB for LPF and for HPF. But not for BH filter. The maximum output in BH output we get at frequency equals to Fc = 7.23KHz. So for the BH output this voltage is our 0dB not -3dB.
This imagine show everything

 

Attachments

steveb

Joined Jul 3, 2008
2,436
For Q1, the answer is that you can't just think blindly about parameter definitions. The idea of "bandwidth" is a concept that is defined relative to the total response, or final output. You need to define new 3dB points in the final output response, then the numerical value of the bandwidth will be clear.

Think about it, what if you shifted the highpass filter cutoff above the lowpass filter cutoff? Would you then have negative bandwidth? No, the response would still have a peak, and there would be points on either side of the peak that are 3 dB down from the peak. It's all relative.
 
Top