Active vs Passive Filter

Question

Could anyone please differentiate active filter from a passive filter? Thanks alot guys..

Answer 1

If you put a load on a passive filter, you could be changing the filter characteristics.

Think of a simple RC filter that is set up as a low pass filter.  If you put a load on the circuit (in parallel with the capacitor) you automatically changed the gain and overall frequency response.

An active filter has a frequency response independent of load.

Yes, it can use devices like op-amps, but they present a low impedance source to the load.

Answer 2

A passive filter doesn't need external power to do its job but an active filter does. Passive filters use components like resistors, capacitors and inductors. Those don't need power. Active filters also use those components plus op amps, which do need power.