Technical Note

9/15

www.rohm.com

2010.10 - Rev.A

© 2010 ROHM Co., Ltd. All rights reserved.

BD3870FS,BD3871FS,BD3872FS,BD3873FS

C1

C2

R3

R4

IN

R1

+

-

R2



(Hz)

R4

R3

R2

C1C2

R4

R3

R1R2

2 π

1











C2

C1

R1

R4

R3

R2

R1R2R4C1C2

Q















(dB)

1

C1

C2

R4

R3

R2

R1

R2R3

1

C1

C2

R4

R3

R2

R1

R4

R3

R2

20log

G(boost)





















●

Description of operations

1) Bass filter

Using external components, center frequencies and Q factors of the bass characteristics are flexible

Fig.5

Standard values of R3, R4 (reference)

(R1=5.6kΩ, R2=390kΩ, C1=C2=0.1µF)

Bass Boost Cut Amount

Resistance (kΩ) * Typ.

R3

R4

0dB

77.64

0

2dB

58.90

18.73

4dB

44.02

33.60

6dB

32.20

45.42

8dB

22.82

54.80

10dB

15.36

62.26

12dB

9.44

68.18

14dB

4.78

72.84

* The actual boost cut amount may deviate from the standard values in some degree.





(

dB)

1

C1

C2

R4

R3

R2

R1

R4

R2(R3

1

C1

C2

R4

R3

R2

R1

R2R3

20log

cut

G





















Fig.6

G

f

F0

G

G