BA3870 View Datasheet(PDF) - ROHM Semiconductor

Part Name

Description

Manufacturer

BA3870

BBS (bass boost system) for radio cassette players

ROHM Semiconductor 

Audio ICs

1. Low range signal system

The transmission of low range signals in Fig. 2 is as shown below.

BA3870

The frequency characteristics of each block are as

shown in Fig. 3, and the gain and cutoff frequency of each

are given by the following equations.

Cutoff frequency of LPF1 : fCL1 =

1

2π S (R4//R5) S C2

(Hz)

Attenuation of LPF1

: GLP1 = 20log R5

R4)R5

(dB)

Gain of Amp A

: GA = 0

(dB)

Attenuation of ATT1

Gain of Amp B

: GATT1 = 20log EVR

R6)EV

: GB = 20log R7)RR6

R7

Cutoff frequency of Amp B: fCL3 =

1

2π S R7 S C3

Cutoff frequency of LPF2: fCL2 =

1

2π S R9 S C4

Gain of Amp C

: GC = 0

(dB)

(dB)

(Hz)

(Hz)

(dB)

Here, R4 = R5 = 2R9 and C2 = C4, thus

fCL1 = fCL2

and the total frequency shows a *12dB / OCT bass

boost as indicated in Fig. 4.

Also, as R11 = 2R10,

GLP1 + GDL = *6 + 6

GLP1 + GDL = 0 (dB)

and thus the total gain during EVR Max. is

GL Max. = GLP1 + GA + GB + GC + GDL

GL Max. = GB (dB)

Gain of Amp D

: GDL = 20log R11

R10

(dB)

426

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