Tool/software: WEBENCH® Design Tools
Hello, I am using the your Filter design tool to design the 2nd order, 6th order Bandpass filter CHEBYSHEV and The design is not tallying with the formulas of cut off frequency. My understanding is that the Fc value for 2nd order is 1/2*pi*sqrt(R1*R2*C1*C2). Please let me know if you agree with this formula or not, also I would like to know the Fc formula for sixth order Bandpass filter as well. Thanks in advance for your help, I look forward to your reply.
NAGA AMAM,
For multiple feedback topology the 2nd order formula is shown below.
For 2nd order Sallen-Key it is shown below.
To design a 6th order filter, it is not an common practice to derive a 6 order transfer function by cascading 2nd order filter 3 times.
We will start with filter response table, and plug the coefficients of each stage into stage transfer function respectively.
Hence, the Filter Design Tool provides W, H, and Q for each stage because you can derive the transfer function
for each stage by using the above equation.
Regards,
Alfred
