Figure 27. Compensation of the input bias current
Iib -
Rin
Rfb
_
VCC+
+
Iib +
R
VCC -
Output
Load
RHF310A
Active filtering
6.5
Active filtering
Figure 28. Low-pass active filtering, Sallen-Key
C1
R1
IN
R2
+
C2
_
OUT
1 kΩ
RG
Rfb
From the resistors Rfb and RG it is possible to directly calculate the gain of the filter in a classic non-inverting
amplification configuration.
AV = g = 1 + R-R---f-g-b-
The response of the system is assumed to be:
Tjω =
Voutjω
Vinjω
=
g
1+2ζ
jω
ωc
+
(jω)2
ωc2
The cut-off frequency is not gain-dependent and so becomes:
DS6201 - Rev 7
page 15/25