Switched-Capacitor Fifth-Order1 Hz to 45 kHz Low-Pass Filter

Low-pass LC-filters in the audio frequency range require huge ferrite-cored inductors. Active filters are also tricky to construct because of the tight tolerance required of the resistors and capacitors. Switched capacitor (SC) technology, however, allows small audio frequency low-pass filters with adjustable corner frequency to be constructed simply. The switching clock frequency used is 100 times higher than the desired corner frequency, so that any residual switching-frequency component at the output can be removed easily using an RC or LC low-pass combination.