EL5156 データシートの表示（PDF） - Intersil
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EL5156 Datasheet PDF : 17 Pages
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EL5156, EL5157, EL5256, EL5257
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).
R1
V1
1kΩ
V2
5V
TUNED POWER
BYPASS NETWORK
L1
10µH
R5
C3
1kΩ 1nF
C5
1nF
C1
1nF
R2
1kΩ C2
1nF
+ V+
- V-
RB
1kΩ
RA
1kΩ
TUNED POWER
BYPASS NETWORK
C5
1nF
R6
1kΩ
L1
10µH
VOUT
R7
1kΩ
C4
1nF
V3
5V
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).
K
=
1
+
-R----B--
RA
VO
=
K
⋅
---------------1-----------------
R2 ⋅ C2S + 1
⋅
VO
-----V----O-------
V-----1----–-----V---i
R1
1
+
-K-----–-----V----1-
R2
+
-V----O-----–-----V----i
-----1-----
=
0
C1S
H 〈 s〉 = -R----1---C-----1---R-----2---C-----2---S----2----+-----(---(--1-----–----K-----)--R----K-1---C-----1----+-----R-----1---C-----2----+-----R-----2--1----C----2----)--s-----+-----1-
H 〈 jw〉 =
-----------------------------------------------------------------------1------------------------------------------------------------------------
1 – w2R1C1R2C2 + jw((1 – K)R1C1 + R1C2 + R2C2)
Holp = K
wo = -----------------1-----------------
R1C1R2C2
Q = ---------------------------------------------1----------------------------------------------
〈 1 – K〉 R-----1---C-----1- + -R----1---C-----2- + R-----2---C-----2-
R2C2 R2C1 R1C1
Holp = K
wo
=
---1-----
RC
Q
=
------1------
3–K
Equations simplify if we let all
components be equal to R = C
FIGURE 35. SALLEN KEY LOW PASS FILTER
12
FN7386.6
July 7, 2009
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