design active filter steps?discuss issue

[sjyatou]

1.firstly select type: butterworth ,chebyshev,or other?
select type base on: passband flat ,stop band rejection ,
2.Select active filter type:
continuous time or discrete time(system demand)
In case :continuous time.
RC ,gm_c ,mosfet_c depend on operation frequency

*****Requestion: now seems that many filters implement in gm_c,even several hundred kHz.
Anyone give some analysis and explaining .

3.whether implement in passive RC firstly

4.then transfer to active elements .

What i know is limited ,please experts give some coaching.
thank you very much .

 

[longstar]

You should also calculate the order to meet the reqirement.
As to high order filter,you can apply cascade or ladder architechture first, then you can apply the active component to replace the L or R.
In fact, we can apply the passive RC filter at the first order to filter the high frequency because the limit f3dB of opa.
And now, i am disigning a video filter.

 

[sjyatou]

You should also calculate the order to meet the reqirement.
As to high order filter,you can apply cascade or ladder architechture first, then you can apply the active component to replace the L or R.
In fact, we can apply the passive RC filter at the first order to filter the high frequency because the limit f3dB of opa.
And now, i am disigning a video filter.

now i am prepare for designing a bandpass filter ,frequency455kHz.
some paper implement it in gm_c .
wish discuss with you about filter design .
select cascade or ladder structure depends on what?