"Chapter 1 - The Op Amp's Place in the World" - HTL Wien 10

or to design for a specific Q:
R 2 R 11 1
2Q
16.6.2 Active Wien-Robinson Filter
Band-Rejection Filter Design
The Wien-Robinson bridge in Figure 16–39 is a passive band-rejection filter with differential
output. The output voltage is the difference between the potential of a constant voltage
divider and the output of a band-pass filter. Its Q-factor is close to that of the twin-T circuit.
To achieve higher values of Q, the filter is connected into the feedback loop of an amplifier.
Figure 16–39. Passive Wien-Robinson Bridge
V IN
VIN C R
Figure 16–40. Active Wien-Robinson Filter
R 4
R 3
R 2
C
R
R
C
2R 1
C R 1
The active Wien-Robinson filter in Figure 16–40 has the transfer function:
A(s)
with
R 2
R 3
1 1 s 2
1 3
·s s2
1
and
R 1
R
R 2
R 4
2R 1
V OUT
V OUT
Active Filter Design Techniques
(16–22)
Comparing the variables of Equation 16–22 with Equation 16–20 provides the equations
that determine the filter parameters:
16-39