EL5156 INTERSIL [Intersil Corporation], EL5156 Datasheet - Page 12

• Manufacturer Part Number: EL5156
• Manufacturer: INTERSIL [Intersil Corporation]

Application Circuits
Sallen Key Low Pass Filter
A common and easy to implement filter taking advantage of
the wide bandwidth, low offset and low power demands of
the EL5152. A derivation of the transfer function is provided
for convenience (See Figure 35).
V
1
1kΩ
R
1
1kΩ C
R
BYPASS NETWORK
BYPASS NETWORK
2
1nF
TUNED POWER
TUNED POWER
2
1nF
C
12
1
1kΩ
R
A
1kΩ
R
B
+
-
EL5156, EL5157, EL5256, EL5257
V+
V-
L
10µH
L
10µH
1kΩ
1kΩ
1nF
1nF
FIGURE 35. SALLEN KEY LOW PASS FILTER
1
1
V
5V
R
C
C
R
V
5V
2
3
5
5
5
6
1nF
1nF
C
C
V
3
4
OUT
R
1kΩ
7
K
V
V
----------------- - 1
H s 〈 〉
H jw
Holp
wo
Q
Holp
wo
Q
O
1
〈
R
=
=
=
–
1
=
=
Sallen Key High Pass Filter
Again this useful filter benefits from the characteristics of the
EL5152. The transfer function is very similar to the low pass
so only the results are presented (See Figure 36).
=
1
V
=
------------------------------------------------------------------------------------------- -
------------ -
3 K
〉
〈
=
=
=
K
i
---------------------------------- -
1 K
-------- -
RC
+
1
–
1
---------------------------------------------------------------------------------------------------------------------------------------------- -
R
R
–
R
------- -
R
⋅
K
K
+
----------------------------------------------------------------------------------------------------------------------------------------------- -
1 w
1
-------------------------------- - V
R
1
B
A
C
–
---------------- -
K V
---------------- -
C
2
〉
1
V
1
R
1
–
⋅
R
O
2
R
C
R
-------------- -
R
2
1
2
R
2
1
2
2S
1
C
1
C
C
C
+
C
2S
2
1
2
+
V
------------------ -
1
+
1
2
R
O
---------- -
C
1
+
⋅
1
1S
2
–
R
-------------- -
R
C
(
V
(
O
1
2
2
1 K
i
C
C
=
+
–
2
1
jw 1 K
0
+
)R
(
(
K
R
-------------- -
R
1
1
C
–
2
1
C
C
1
2
1
+
)R
Equations simplify if we let all
components be equal to R = C
R
1
1
C
C
1
2
+
+
R
R
1
21
C
C
2
+
2
)s
September 13, 2007
R
2
+
C
1
2
)
FN7386.5