Publisher Summary Integrated Circuit (IC) filter, a continuous time filter, has a fixed frequency response that is determined at the design stage and set by external resistors. Switched capacitor filters are generally noisier than their continuous-time counterparts. This is mainly because of the switching process; signals at the switching frequency and other spurious signals that appear at the filter's output. Many semiconductor manufacturers produce filter ICs. Filter ICs from three companies―Maxim, Texas Instruments, and Linear Technology are described with practical design examples. Problems encountered with these types of filter are also described. The benefits include being able to make the filter cutoff programmable or adjustable. A frequency synthesizer that derives a sine wave signal from a clock-driven logic circuit is described. The filtering of its output can be carried out in one of the two ways―with a fixed frequency filter, if the clock frequency is fixed; and with a tuned switched capacitor filter, which tracks the frequency of the output signal, if the clock frequency is tunable.