Butterworth filters have the following characteristics:
The advantage of Butterworth filters is their smooth, monotonically decreasing frequency response. The following figure shows the frequency response of a lowpass Butterworth filter.
As shown in the previous figure, after you specify the cut-off frequency of a Butterworth filter, the steepness of the transition is proportional to the filter order. Higher order Butterworth filters approach the ideal lowpass filter response.
Butterworth filters do not always provide a good approximation of the ideal filter response because of the slow roll-off between the passband and the stopband.