LM358, LM258, LM2904, LM2904V
Figure 12. Function Generator
Figure 13. Multiple Feedback Bandpass Filter
1
2
Triangle Wave
Output
V
=
V
R2
V
ref
CC
CC
R3
C
300 k
C
V
+
R1
ref
R3
V
–
1/2
in
+
1/2
LM358
1/2
LM358
V
75 k
O
LM358
–
R1
100 k
Square
Wave
Output
+
CO
CO = 10 C
–
R2
V
ref
C
V
ref
1
2
V
=
V
CC
ref
R
f
R1 + R
R2 R1
C
f =
if, R3 =
Given:
f = center frequency
o
4 CR R1
R2 + R1
f
A(f ) = gain at center frequency
o
Choose value f , C
o
Q
Then: R3 =
π
f C
o
R3
2 A(f )
R1 =
R2 =
o
R1 R3
2
4Q R1 –R3
Q
f
o o
For less than 10% error from operational amplifier.
Where f and BW are expressed in Hz.
< 0.1
BW
o
If source impedance varies, filter may be preceded with voltage
follower buffer to stabilize filter parameters.
6
MOTOROLA ANALOG IC DEVICE DATA
MOTOROLA [ MOTOROLA ]
