LM324, LM324A, LM224, LM2902, LM2902V, NCV2902
V
ref
=
V
ref
1
V
2
CC
+
1/4
Triangle Wave
Output
R3
75 k
R1
100 k
V
ref
R
f
f =
R1 + R
C
4 CR
f
R1
if R3 =
R2 R1
R2 + R1
R2
300 k
+
1/4
LM324
-
V
CC
C
Square
Wave
Output
R1
V
in
R2
V
ref
C
R3
-
1/4
LM324
-
C
O
V
O
CO = 10 C
1
V
ref
= 2 V
CC
C
LM324
+
Figure 16. Function Generator
Figure 17. Multiple Feedback Bandpass Filter
Given:
f
o
= center frequency
A(f
o
) = gain at center frequency
Choose value f
o
, C
Then:
R3 =
R1 =
R2 =
Q
p
f
o
C
R3
2 A(f
o
)
R1 R3
4Q
2
R1 - R3
Q
o
f
o
BW
< 0.1
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.
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