
13 6
Analog Electronics
calculator. At ω,, = 1 the response of the second-
order section is unity since D = Q = \ , i.e. for this
value of damping the peak is entirely to the left of
the corner frequency, as can be seen in Figure 2.8b
for the curve /? = 1, corresponding to Q = \ for
our active filter. Thus the complete third-order
filter's response at the corner frequency is —3 dB,
the same as the first-order section alone. However
high the order of a Butterworth filter, the
bandwidth is still defined as that frequency at
which the response is -3 dB relative to the low-
frequency response - or to the high-frequency
response in the case of a high-pas ...