For example, a moving average filter will have a finite impulse response. There are some exceptional cases where the presence of feedback structure may result in finite impulse response.
Due to the presence of feedback elements, the impulse response of the filter may not become zero beyond certain point, but continues indefinitely and hence the name Infinite Impulse Response (IIR) filter. When, the filter structure is characterized by the presence of feedback elements.It provides linear phase characteristic in the passband. The impulse response of such filter dies out (becomes zero) beyond certain point of time and it is classified as Finite Impulse Response (FIR) filter. When, there is no feedback in the filter structure, no poles in the pole-zero plot (in fact all the poles sit at the origin).
Two types of filter can manifest from the given transfer function above. In other words, the design process also involves choosing the number and location of the zeros zeros ( ) and poles ( ) in the pole-zero plot. Examples include how much ripples allowed in passband, stop band etc.,