Operational Amplifier Circuits

Introduction

to

Active

Filters

63

narrow bandwidths,

if the two

break frequencies

are

sufficiently close

to

each

other,

the

maximum gain will

be

less than

(-/jy/^Xsee

also Section 5.3.3).

5.3 Second-Order Active

Filters

As explained

in

Section 5.1, second-order active filters, based

on a

single oper-

ational amplifier,

are

useful both

in

their

own

right

and as

building blocks

for

higher-order filters. Although many configurations

are

possible, that shown

in

general form

in

Figure

5-5 is

widely used. The components selected

for

each

Z

determine

the

form

of the

filter response (low, high,

or

band pass),

as

will

be

shown later.

In

most cases

(th ...