LM258, LM358, LM358A, LM2904, LM2904A, LM2904V, NCV2904
Vref
=
1
2
VCC
Vref
Triangle Wave
Output
+
1/2
R3
LM358
−
75 k
R1
C
Vref
R2
300 k
100 k
+
1/2
LM358
−
Rf
f = R1 + RC
R2 R1
if, R3 =
4 CRf R1
R2 + R1
Figure 15. Function Generator
VCC
C
R3
R1
C
Vin
−
1/2
LM358
R2
+
Vref
VO
CO
CO = 10 C
Vref =
1
2
VCC
Square
Wave
Output
Given: fo = center frequency
A(fo) = gain at center frequency
Choose value fo, C
Then:
R3 =
Q
p fo C
R3
R1 = 2 A(fo)
R2
=
R1 R3
4Q2 R1 −R3
For less than 10% error from operational amplifier. Qo fo < 0.1
BW
Where fo and BW are expressed in Hz.
If source impedance varies, filter may be preceded with voltage
follower buffer to stabilize filter parameters.
Figure 16. Multiple Feedback Bandpass Filter
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