LM358, LM258, LM2904, LM2904V
Figure 12. Function Generator
1
Vref = VCC
2
Vref
+
1/2
Figure 13. Multiple Feedback Bandpass Filter
VCC
C
Vin
Square
Wave
Output
R1
C
R3
1/2
Triangle Wave
Output
R3
75 k
R1
Vref
Rf
f =
R1 + RC
4 CRf R1
if, R3 =
R2 R1
R2 + R1
100 k
R2
300 k
+
1/2
–
LM358
–
LM358
–
R2
Vref
LM358
+
VO
CO
CO = 10 C
1
Vref = 2 VCC
C
Given:
fo = center frequency
A(fo) = gain at center frequency
Choose value fo, C
Then:
R3 =
Q
π
fo C
R3
R1 =
2 A(fo)
R2 =
R1 R3
4Q2 R1 –R3
Qo fo
< 0.1
BW
For less than 10% error from operational amplifier.
Where fo and BW are expressed in Hz.
If source impedance varies, filter may be preceded with voltage
follower buffer to stabilize filter parameters.
6
MOTOROLA ANALOG IC DEVICE DATA
MOTOROLA [ MOTOROLA, INC ]
