IIR and FIR filters are types of digital filters. IIR filters are infinite impulse response filters that are recursive, can simulate analog filters, and require less memory but can be unstable. FIR filters are finite impulse response filters that are non-recursive, always stable, require more memory but ensure linear phase response and are preferred over IIR filters for many applications. The document discusses the key differences between IIR and FIR filters in their characteristics, uses, and computational efficiency.

1. Difference Between IIR and FIR Filters
• Categorized under Physics,Science | Difference Between IIR and FIR Filters
IIR vs FIR Filters
IIR filters are difficult to control and have no particular phase, whereas FIR filters make a linear
phase always possible. IIR can be unstable, whereas FIR is always stable. IIR, when compared to
FIR, can have limited cycles, but FIR has no limited cycles. IIR is derived from analog, whereas
FIR has no analog history. IIR filters make polyphase implementation possible, whereas FIR can
always be made casual.
FIR filters are helpful to achieve fractional constant delays. #MAD stands for a number of
multiplications and additions, and is used as a criterion for an IIR and FIR filter comparison. IIR
filters require more #MAD when compared to FIR, because FIR is of a higher order in
comparison to IIR, which is of lower order, and uses polyphase structures.
FIR filters are dependent upon linear-phase characteristics, whereas IIR filters are used for
applications which are not linear. FIR’s delay characteristics is much better, but they require
more memory. On the other hand, IIR filters are dependent on both i/p and o/p, but FIR is
dependent upon i/p only. IIR filters consist of zeros and poles, and require less memory than FIR
filters, whereas FIR only consists of zeros. IIR filters can become difficult to implement, and
also delay and distort adjustments can alter the poles & zeroes, which make the filters unstable,
whereas FIR filters remain stable. FIR filters are used for tapping of a higher-order, and IIR
filters are better for tapping of lower-orders, since IIR filters may become unstable with tapping
higher-orders.
FIR stands for Finite IR filters, whereas IIR stands for Infinite IR filters. IIR and FIR filters are
utilized for filtration in digital systems. FIR filters are more widely in use, because they differ in
response. FIR filters have only numerators when compared to IIR filters, which have both
numerators and denominators.
Where the system response is infinite, we use IIR filters, and where the system response is zero,
we use FIR filters. FIR filters are also preferred over IIR filters because they have a linear phase
response and are non recursive, whereas IIR filters are recursive, and feedback is also involved.
FIR cannot simulate analog filter responses, but IIR is designed to do that accurately. IIR’s
impulse response when compared to FIR is infinite.

2. The high computational efficiency of IIR filters, with short delays, often make the IIR popular as
an alternative. FIR filters have become too long in digital feedback systems, as well as in other
applications, and cause problems.
Summary:
1. IIR is infinite and used for applications where linear characteristics are not of concern.
2. FIR filters are Finite IR filters which are required for linear-phase characteristics.
3. IIR is better for lower-order tapping, whereas the FIR filter is used for higher-order tapping.
4. FIR filters are preferred over IIR because they are more stable, and feedback is not involved.
5. IIR filters are recursive and used as an alternate, whereas FIR filters have become too long and
cause problems in various applications.
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