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Chaining Filters Created by Filter Wizard

Question asked by groger on Aug 30, 2015
Latest reply on Sep 5, 2015 by groger

Hi,

 

I have a design where there is a very high interfering frequency level close to a frequency of interest. I need the filter output for an ADC input, biased/centered at 1.65V. I created an LPF using the filter wizard, with low ringing and fast settling. Also, I need a gain of about 50 to 60db

I selected a Butterworth-Bessel with a factor of 0.9. It is 5 stages, using the AD8616. Ultimately, the total stop band I require is about 80 to 100dB.

 

It's clear a single 5 stage op-amp will not give me the gain and the suppression I require. What must I be aware of if I want to chain 2 such designs together? From what I understand, here's what I think must be considered:

 

-input signal overloading 2nd 5 stage filter

-DC offset cascading through and causing uneven center rail swing

 

Can anyone please explain if there's more, or perhaps a better way to approach this.

Thanks!

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