Filters are semiconductor products which perform basic single processing functions to remove unwanted frequencies, also referred to as noise. Filters are available in a number of different types, such as passive and active, analog and digital, linear and nonlinear. The most well know filters are low-pass, high-pass, band-pass and band-stop. Filters are found in a variety of different applications but are most popular in audio and multimedia applications. A filter is an electronic network where the output voltage, current, or power varies in a predictable way with the input frequency. Filters can be designed to pass high frequencies, block low frequencies, pass only low frequencies, pass/block only a specific band of frequencies, or any other combination.