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

16.4.1 First-Order High-Pass Filter
Active Filter Design Techniques
High-Pass Filter Design
Figure 16–25 and 16–26 show a first-order high-pass filter in the noninverting and the inverting
configuration.
V IN
Figure 16–25. First-Order Noninverting High-Pass Filter
V IN
Figure 16–26. First-Order Inverting High-Pass Filter
The transfer functions of the circuits are:
A(s)
1 R2 R3 1 1
· cR1C1 1 s
C 1
C 1
R 1
R 1
R 3
R 2
R 2
and
V OUT
V OUT
A(s)
R2 R1 1 1
· cR1C1 1 s
The negative sign indicates that the inverting amplifier generates a 180° phase shift from
the filter input to the output.
The coefficient comparison between the two transfer functions and Equation 16–6 provides
two different passband gain factors:
A 1 R 2
R 3
and
A R 2
R 1
while the term for the coefficient a 1 is the same for both circuits:
a 1
1
cR 1 C 1
16-23