LM358, LM258, LM2904, LM2904A, LM2904V, NCV2904
V
CC
C
V
in
R1
C
R3
1/2
−
R2
V
ref
LM358
+
V
O
CO
CO = 10 C
1
V
ref
= 2 V
CC
Given:
f
o
= center frequency
A(f
o
) = gain at center frequency
Choose value f
o
, C
V
ref
=
V
ref
1
V
2
CC
+
1/2
Triangle Wave
Output
R3
75 k
R1
V
ref
R
f
f =
R1 + R
C
4 CR
f
R1
if, R3 =
R2 R1
R2 + R1
100 k
R2
300 k
+
1/2
Then:
R3 =
R1 =
R2 =
Q
p
f
o
C
R3
2 A(f
o
)
R1 R3
4Q
2
R1 −R3
Q
o
f
o
< 0.1
BW
LM358
−
LM358
−
C
Square
Wave
Output
For less than 10% error from operational amplifier.
Where f
o
and BW are expressed in Hz.
If source impedance varies, filter may be preceded with voltage
follower buffer to stabilize filter parameters.
Figure 15. Function Generator
Figure 16. Multiple Feedback Bandpass Filter
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