Interface - Filters - ActiveAn active filter is a type of filter that uses active components, such as transistors or operational amplifiers, to amplify and shape the signal in order to remove unwanted frequencies. Active filters are commonly used in EMI (electromagnetic interference) optimization in cables, as well as in a variety of other applications. Unlike passive filters, which only use passive components such as resistors and capacitors, active filters are able to provide gain and can operate over a wider frequency range. However, they also require a power source in order to function, which makes them more complex and expensive than passive filters.