Stopband

A stopband is a band of frequencies, between specified limits, through which a circuit, such as a filter or telephone circuit, does not allow signals to pass, or the attenuation is above the required stopband attenuation level.

A band-stop filter has one stopband, specified by two non-zero and non-infinite corner frequencies.

The difference between the limits in the band-stop filter is the stopband bandwidth, which usually is expressed in hertz.

The shape factor of a bandpass filter is the relationship between the 3 dB bandwidth, and the difference between the stopband limits.

This article incorporates public domain material from Federal Standard 1037C.

Frequency response of an example bandpass filter. The frequencies between a stopband and a passband define the transition band.