About active filter

An active filter is an electronic filter that uses active components such as transistors, operational amplifiers, or other amplifying elements, in addition to passive components such as capacitors and inductors, to filter a signal. Active filters are able to provide steeper roll-off characteristics and greater flexibility than passive filters, but they require a power source to operate. They are often used in electronic circuits to remove unwanted frequencies or to improve the signal-to-noise ratio.