Editing Infinite impulse response (section)

== Advantages and disadvantages==
The main advantage digital IIR filters have over FIR filters is their efficiency in implementation, in order to meet a specification in terms of passband, stopband, ripple, and/or roll-off. Such a set of specifications can be accomplished with a lower order (''Q'' in the above formulae) IIR filter than would be required for an FIR filter meeting the same requirements. If implemented in a signal processor, this implies a correspondingly fewer number of calculations per time step; the computational savings is often of a rather large factor.

On the other hand, FIR filters can be easier to design, for instance, to match a particular frequency response requirement. This is particularly true when the requirement is not one of the usual cases (high-pass, low-pass, notch, etc.) which have been studied and optimized for analog filters. Also FIR filters can be easily made to be  [[linear phase]] (constant [[group delay]] vs frequency)—a property that is not easily met using IIR filters and then only as an approximation (for instance with the [[Bessel filter]]). Another issue regarding digital IIR filters is the potential for [[limit cycle]] behavior when idle, due to the feedback system in conjunction with quantization.