BA3870 View Datasheet(PDF) - ROHM Semiconductor

Part Name

Description

Manufacturer

BA3870

BBS (bass boost system) for radio cassette players

ROHM Semiconductor 

Audio ICs

2. High-range signal system

The transmission of high frequency signals in Fig. 2

is as shown below.

BA3870

The frequency characteristics of each block are shown

in Fig. 5, and the gain and cutoff frequency of each are

given by the following equations.

1

Cutoff frequency 1 of HPF: fCH1 =

2π S (R1)R2) C1

(Hz)

(R2)R3)

Cutoff frequency 2 of HPF: fCH2 = 2π S (R1R2)R2R3 )R1R3) C1(Hz)

Attenuation of HPF in

: GHP1 = 20log

R3

frequency range f t fCH1

R2)R3

(dB)

Attenuation of HPF in

: GHP2 = 20log

R3

frequency range fCH2 t f

R1//R2)R3

(dB)

Gain of Amp D

: GDH = 20log R10)R11

R10

(dB)

3. Combination of frequency characteristics

By combining the low-range characteristics (Fig. 4)

and the high-range characteristics (Fig. 6), ideal BBS

characteristics can be obtained as shown in Fig. 7.

The total frequency characteristics show a +6dB / OCT

treble boost as shown in Fig. 6.

Also, R11 = 2R10, thus

GDH = +9.5 (dB)

and the total gain GH1 in the f t fCH1 frequency range is

GH1 = GHP1 + GDH

GH1 = GHP1 + 9.5 (dB)

The total gain GH2 in the fCH2 t f frequency range is

GH2 = GHP2 + GDH

GH2 = GHP2 + 9.5 (dB)

427

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