Analog filter wizard query

Thread Starter

fbp

Joined Aug 9, 2023
30
Has anyone used the analog filter wizard website to design their filters? Does it work practically as shown on the website when we design it from this website? When we mention our requirement in terms of BW, centre frequency and stop band, the filter is usually designed as 10th Order Butterworth filters (since I need to use a butterworth filter). The order of the filter is very high.
 

crutschow

Joined Mar 14, 2008
34,409
the filter is usually designed as 10th Order Butterworth filters (since I need to use a butterworth filter). The order of the filter is very high.
It builds it according to your requirements, which apparently include a very steep rolloff for the stopband which in turn, requires a high filter order.
If you want to use fewer filter orders, than you will need to relax your requirements.
Is the rolloff a real system requirement is it just some value that sounds good?
Why does it have to be a Butterworth filter?
 

Thread Starter

fbp

Joined Aug 9, 2023
30
I choose the Butterworth filter since I need a flat response for the passband and avoid oscillation that occurs in other filters.
While changing the filter settings, I was not able to get a low order Butterworth filter for various BPF values. Some combinations of settings do not work.

My requirement is as follows:
Frequency: 500kHz (Freq of interest) But I am using a BPF to attenuate the low frequencies
Input amplitude variation: 6Vpp (-3V to +3V input amplitude) which should me the same range across the output
Gain = 1
I am looking to choose an IC that meets these specifications.


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crutschow

Joined Mar 14, 2008
34,409
My requirement is as follows:
I see no requirement for how fast the filter should rolloff outside the passband, which determines the filter order required.
What is the frequency and amplitude of the low frequencies and high frequencies outside the passband, and how much do you need to attenuate them?

And if you want an adjustable filter, you may need to go to a digital filter.
 
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