(-60dB within 20Hz)Steep roll-off LPF with 30Hz bandwidth

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blurryeyes81

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roll off steep

Hi guys,
I'm currently looking into designing a LPF with specifications of a 30Hz bandwidth and an ultra steep roll-off. ie. attenuation of 60dB within a range of 20Hz for power supply noise rejection. THe LPF is to be used as part of an instrumentational amplifier IC and ideally would like to have all components on-chip.

Any suggestions as to how best to implement the LPF? Gm-C filter? Elliptic filter?

Thanks!
 

rolloff bandwidth

I don't think you can build this filter on-chip by any continuous-time filtering: just think about the extremely large time constant needed (i.e. 30Hz!). You may get away by doing switch-cap filter, but this definitely defies your purpose of power supply filtering.

I bet the system spec you have is not valid or practical to begin with. There should be better alternative.
 

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