Active filters use amplifying elements, especially op amps, with resistors and capacitors in their feedback loops, to synthesize the desired filter characteristics. Active filters can have high input impedance, low output impedance, and virtually any arbitrary gain.
They are also usually easier to design than passive filters. Possibly their most important attribute is that they lack inductors, thereby reducing the problems
associated with those components.
I am also going with active filter but while designing i found that with smaller Q factor the passband is less.
since our application is of higher frequency i am not getting flat response.
Can u suggest any artical which helps in selecting correct opamp for that.
vasu,
If you go the active route, the circuit must have considerable (i.e. >100) loop gain at the highest frequency of interest , in your case 800KHz. Otherwise the actual response will differ considerably from the ideal response.
~
Some disadvantages of passive filters:
Hard to design high Q inductors.
Filter must be designed for specific source and load impedances.
Regards,
Kral