BA3308 Datasheet BA3308F-E2, BA3308FV-E2, BA3308 | P4-P6

Technical Note

4/9

BA3308F,BA3308FV

www.rohm.com

2012.06 - Rev.C

●Electrical characteristic curves (Reference data)

Fig.2 Quiescent current vs. Fig.3 Quiescent current vs. Fig.4 Voltage gain vs. frequency

power supply voltage ambient temperature

Fig.5 Total harmonic distortion vs. Fig.6 Voltage gain vs. Fig.7 Closed loop voltage gain vs.

frequency supply voltage ambient temperature

Fig.8 Input conversion noise voltage Fig.9 Channel separation vs. Fig.10 ALC characteristics

vs. signal source resistance frequency

Fig.11 Input/output characteristics Fig.12 Maximum output voltage vs. Fig.13 Maximum output voltage vs.

power supply voltage load resistance

Technical Note

5/9

BA3308F,BA3308FV

www.rohm.com

2012.06 - Rev.C

●Description of operations

1. Recording

1) Record amplifier

2) ALC

Fig.5

BA3308

Cont

ch2

(ch1)

ch2

(ch1)

ch1

(ch2)

2 (8) 1 (9) 3 (7) 5

3.9k

10F

INPUT

39

18k

1M

100F

10F

22F

OUTPUT

R

1

(R

2

)

R

3

(R

4

)

R

5

(R

6

)

R

7

(R

8

)

C

1

(C

2

)

C

3

(C

4

)

C

5

(C

6

)

C

7

(C

8

)

Fig.14

The BA3308F/FV has an on-chip signal rectifier and electronic

volume needed for ALC. The signal rectifier compares the direct

current output voltage that is superposed in the output stage (1, 7pin)

signal to the reference voltage 4.5V

F (≒3V; 1VF is approximately

0.7V) in the comparator circuit and if the output voltage is higher, it

turns the comparator ON to charge the smoothing capacitor C

7.

Since the operation point of the output stage of amplifier ch1 and ch2

is fixed at 3V

F, the comparator turns ON when the peak value of the

signal output voltage is 1.5VF (effective value approx. 0.75V). Once

the direct current signal for electronic volume is controlled, ALC

operation starts. The electronic volume, which is connected between

the input line (13, 9pin) and GND, causes the input signal to

attenuate according to the ratio of the external resistance (R

1, R2) to

the resistance value of the electronic volume. The ALC range varies

according to the values of R

1 and R2. For small ALC variation the

S/N will determinate an adequate ALC range is obtained by applying

several k of the R

1 and R2. The attack time and recovery time of

ALC are set according to C7 and R7 of 4pin. If the time constants

(C

7, R7) are large, the recovery time will be long and as C7 becomes

smaller, and the attack time will be shorter.

The BA3308F/FV amplifier of ch1 and ch2 input stage

(13pin, 9pin) can be direct coupled or use coupling

capacitors (C1/C2). The voltage gain of the record amplifier

is determined by G

V=R5/R3. The R5/R6, and C3/R3 regulate

control of the pop noise that occurs at power-on (see

“Cautions on use”) and direct current bias fed back is set by

R5/R6 and C5/C6 at the output stage.

13(9)

11(10) 1 (7)

4

Fig.6

ch2

(ch1)

ch2

(ch1)

ch1

(ch2)

ContComp

BA3308

3 (7)

5

2 (8)

4.5VF

VOUT (DCAC)

3V

F

R

7

C

7

R

1

(R

2

)

Fig.15

1 (7) 4 13(9)

Technical Note

6/9

BA3308F,BA3308FV

www.rohm.com

2012.06 - Rev.C

2. On playback

.

Since amplifier ch1 and ch2 are used as a NAB equalizer

amplifier at playback, a time constant circuit is established in

the NF section (1-11pin, 7-10pin) to obtain NAB

characteristics. The voltage gain at this time is determined by

the following formula:

G

V = │R11＋R9/ (│＋jC9・R9)│/R3

Obtain the necessary gain by regulating the (power-on pop

noise prevention) NAB time constant circuit in the same way

when regulating the gain at recording stage. The operating

point of the output stage (1,7pin) is fixed at 3VF.

Accordingly, even if V

CC is raised to 5V or more, as in the

V

MAX-VCC characteristic (Fig.13), the maximum output voltage

does not rise above 1.2V (Typ.). 4pin is grounded at playback

since ALC is not needed. For better signal-to-noise ratio

characteristics at playback, don’t use R

1 and R2, which are

attached to the input pin (13pin, 9pin).

Fig.7

A1

BA3308

2 (8)

10

μ

F

0.027

μ

F

39



1 (9)

3 (7)

5

INPUT

OUTPUT

R

3

(R

4

)

C

9

(C

10

)

(C

6

)

C

5

10

μ

F

(C

2

)

C

1

100

μ

F

(C

4

)

C

3

R

11

(R

12

)

4.3k



R

9

(R

10

)

120k



13(9)

11(10)

1 (7)

4

Fig.16

BA3308

BA3308

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