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# What is the difference between FIRs and IIRs ?

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#### Resistance

##### Member level 4
difference between fir and iir filters

Hi friends,

Can u tell me the major diff between FIR's and IIR's.. plus the practical applications where FIRs are used.

#### aho1363

##### Newbie level 4
difference between the fir and iir

#### ziyas

##### Member level 1
iir filter transient response

Resistance said:
Hi friends,

Can u tell me the major diff between FIR's and IIR's.. plus the practical applications where FIRs are used.
The choice between an FIR filter and an IIR filter depends on the importance to design problem of the advantages of each type. IIR filters, for example, have the advantage that a variety of frequency-selective filters can be design using closed form design formulas. That is, once the problem has benn specified in terms appropriate for a given approximation method.(Butterworth(maximally flat filters) ,Chepyshev,or elliptic), the the order of the filter that will meet the specifications can be computed, and the coefficients(or poles and zeros) of the discrete time filter can be obtained by straightforward substitution into a set of design.
In contrast FIR filters can have a generally linear phase. However, closed form design equations do not exist for FIR filters.
Also we must look the money in many cases, the linear phase avilable with an FIR filter may be well worth the extra cost, and in applications such as decimation or interpolation, FIR filteers may be just as efficient as IIR filters.

#### elecs_gene

##### Member level 2
FIR's and IIR's

hi
the major difference between FIR & IIR ,is not only LINEAR PHASE ,but also the stability issues come into play.IIR is not always stable whereas FIR is.also,IIR has some problems like limit cycle oscillations.

regards

### Resistance

Points: 2

#### mystique_unbound

##### Junior Member level 3
Re: FIR's and IIR's

IIR filters are highly helpful in in getting perfect filter characteristics but they are hard to implement . They have poor transient response and also high shootups .
Since IIR filters result in nonlinear phase cascade form realization is not enough . we need to use feedback and non linearity in phase obviously make our signal depen on the previous samples .
whereas FIR filters are of linear phase which is easy to implement and also ithas one disadvantage at the time response due to sharp cut off by the sampling pulse . so use Kaiser filter which has efficient time response and also it is flexible

### Resistance

Points: 2

#### kachuisa

##### Junior Member level 1
Re: FIR's and IIR's

I think nobody can explain clearly, i should read a basic book

#### ee_expert2000

##### Member level 4
Re: FIR's and IIR's

FIR filters can have linear phase but the orders are higher.
check for type 1,2,3,4 filters to see their responses' specification.
they are good if you have specifications on the magnitude response.
on the other side, IIR filters are good if you have something to do with phase.
they also have less order but may not always be stable.
so you have a trade off.

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