
Chapter
6
Active signal processing in
the
frequency
domain
In Chapter 2 we looked at passive circuits whose
response was frequency selective, and in Chapter 3
we discussed operational amplifiers. In this
chapter we bring these two items together and look
at active filters and related topics. Active filters are
preferred at audio frequencies since they enable all
types of filters and phase equalizers to be realized
with suitable combinations of resistors, capacitors
and opamps. Thus the inductors that would be
necessary for a passive filter can be dispensed with
entirely; this is a real blessing since good quality
high-value inductors, such