# Extensive Definition

A stopband is a band of
frequencies, between specified limits, in which a circuit,
such as a filter
or telephone circuit,
does not let signals through, or the attenuation is above the
required stopband attenuation level. Depending on application, the
required attenuation within the stopband may typically be a value
between 20 and 120 dB
higher than the nominal passband attenuation, which often is 0
dB.

The lower and upper limiting frequencies, also
denoted lower and upper stopband corner
frequencies, are the frequencies where the stopband and the
transition
bands meet in a filter specification. The stopband of a
low-pass filter is the frequencies from the stopband corner
frequency (which is slightly higher than the passband 3dB cut-off
frequency) up to the infinite frequency. The stopband of a
high-pass filter consists of the frequencies from 0 Hertz to a
stopband corner frequency (slightly lower than the passband cut-off
frequency).

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.

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

## See also

- Passband
- Band-stop filter
- Band gap in solid state physics
- Band rejection

stopband in Russian: Полоса подавления

stopband in Swedish: Stoppband