Datasheet BA7760F, BA7760 Datasheet (ROHM)

1

Multimedia ICs

Microphone Amplifier

BA7760 / BA7760F

The BA7760 and BA7760F are dual microphone amplifiers designed for audio signal amplification. These are low
noise amplifiers with a low -122dBV (typically) equivalent input noise voltage. Each IC has an internal mixer buffer
amplifier for the mixing of signals from two channels. When used with the BA7725S or BA7725FS, the BA7726AS or
BA7726AFS and BU9252S or BU9252F, these ICs simplify the configuration of digital echo systems with two inputs
(for karaoke duets, for instance).

•

Features

1) Internal 2-channel low noise microphone amplifier.

2) Internal mixer buffer amplifier with mute function.

3) Available in 2 types of packages: DIP 14-pin or SOP
14-pin.

•

Applications

Audio equipment with karaoke features, VCRs, LDs, etc.

•

Absolute maximum ratings (Ta = 25°C)

Parameter Symbol Limits Unit

Applied voltage 15 V

BA7760

mW

BA7760F
Operating temperature °C
Storage temperature °C

V

CC

Power
dissipation

600

∗

1

450

∗

2

Pd

Topr – 25 ~ + 75

– 55 ~ + 125Tstg

∗

1 Unmounted. Reduced by – 6.0mW for each increase in Ta of 1°C over 25°C.

∗

2 Unmounted. Reduced by – 4.5mW for each increase in Ta of 1°C over 25°C.

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Recommended operating conditions

Parameter Symbol Limits Unit

Power supply voltage V

CC 6 ~ 14 V

2

Multimedia ICs BA7760 / BA7760F

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Pin descriptions

Pin name Pin type
1 Ripple filter
2GND GND —
3 MIC IN ( + ) Ch1 CH1 microphone amplifier input ( + )
4 MIC IN ( – ) Ch1 CH1 microphone amplifier input ( – ) Base (NPN)
5 CH1 microphone amplifier fc Base (NPN) ~ 450Ω
6 CH1 microphone amplifier output Push-pull
7 Mixer buffer input
8 Mixer buffer output Push-pull
9 CH2 microphone amplifier output Push-pull

10 CH2 microphone amplifier fc Base (NPN) ~ 450Ω
11 MIC IN ( + ) Ch2 CH2 microphone amplifier input ( – ) Base (NPN)
12 MIC IN ( – ) Ch2 CH2 microphone amplifier input ( + )
13 Mute control Fig.1
14 —

RIPPLE FILTER

FILTER Ch1

MIX IN

MIC OUT Ch1

MIX OUT
MIC OUT Ch2
FILTER Ch2

MUTE CTRL
V

CC VCC

Base (NPN) // 15kΩ

Base (NPN) // 120kΩ

Base (NPN) // 65kΩ

Base (NPN) // 120kΩ

Pin No. Function

∗

“Parallel” and “series” respectively refer to parallel and series insertion. All figures are standard values.

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Block diagram

+

–

–

+

–

+

8

9

10

11

12

13

14 1

2

3

4

5

6

7

GND

MIX IN

MIC OUT Ch1

FILTER Ch1

RIPPLE FILTER

MIX OUT

MUTE CTRL

V

CC

MIC IN Ch1 ( – )

MIC IN Ch1 ( + )

MIC AMP CH 1
MIC AMP CH 2

MIX BF

MIC OUT Ch2

FILTER Ch2

MIC IN Ch2 ( + )

MIC IN Ch2 ( – )

3

Multimedia ICs BA7760 / BA7760F

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Electrical characteristics (unless otherwise noted, Vcc = 12V, Ta = 25°C)

Parameter Symbol Min. Typ. Max. Unit

Supply current I

q 3.65 4.87 6.09 mA

〈MIC AMP (GVC = 36dB, f = 1kHz)〉

55.0 65.0 — dB VIN = – 70dBV
— – 122 – 114 dBV Rg = 2.2kΩ, DIN AUDIO

— 0.008 0.1 %

V

IN = – 40dBV

B.W. = 0.4 ~ 30kHz

8.3 10.4 — dBV

THD = 1%
B.W. = 0.4 ~ 30kHz

92 123 — kΩ V

IN = – 40dBV, 100kΩAttenuation

V

IN = – 10dBV, 50kΩAttenuation

— – 86 – 78 dBV

V

IN = – 36dBV

R

g = 2.2kΩ, DIN AUDIO

– 0.7 0 0.7 dB V

IN = – 10dBV

— –110 – 100 dBV R

g = 2.2kΩ, DIN AUDIO

— 0.002 0.07 %

V

IN = – 10dBV

B.W. = 0.4 ~ 30kHz

8.3 10.5 — dBV

THD = 1%
B.W. = 0.4 ~ 30kHz

50.0 66.5 — kΩ
— – 110 – 100 dBV V

IN = – 10dBV, DIN AUDIO

2.12 2.62 3.12 V

VnM

THDM

VomM

ZinM

CTM

GVB
VnB

THDB

VOMB

ZinB

MTB

VTHMUTE

Open loop voltage gain
Input conversion noise

Distortion

Maximum output level
Input impedance
Crosstalk

〈MIX BF (f = 1kHz)〉

Voltage gain
Output residual noise

Distortion

Maximum output level
Input impedance

Mute level
Mute threshold voltage

Conditions

—

—

G

VOM

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Input / output circuits

Fig. 1

40kΩ

MUTE CTRL 13

4

Multimedia ICs BA7760 / BA7760F

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Measurement circuit

+
–

MIX BF

8

9

10

11

12

13

14 1

2

3

4

5

6

7

–+ –+

+

4.7µF

5kΩ

2.2kΩ

150pF

13.9kΩ

1MΩ

220Ω

+

4.7µF

2.2kΩ

22µF

+

+

+

Ch1

Ch1

220Ω

2.2kΩ

4.7µF

+

+

+

150pF

13.9kΩ

1MΩ

Ch2

10kΩ

5kΩ

10µF

Ch2CTRL

MUTE

470µF

47µF

470µF

47µF

MIC IN

MIX OUT

MIC OUT

MIX IN MIC OUT

MIC IN

BA7760 / F

MIC AMP Ch2

MIC AMP Ch1

V

CC

Fig. 2

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Circuit operation (Refer to “Application Example”)
The BA7760 and BA7760F are dual microphone ampli­fiers. The audio signals from the microphones are input
to pins 3 and 12. The gain at this time is determined by
attached resistors R3 / R4 and R6 / R7. By attaching
capacitors to pins 5 and 10, the microphone amplifiers
can be given frequency characteristics like those
shown below.

(Note: The attached component numbers are those used in “Application
Example.”)

60dB

40dB

20dB

0dB

– 20dB

1kHz 10kHz 100kHz 1MHz 10MHz100MHz

VOLTAGE GAIN : GV (dB)

C = 150pF

C = 0

361

163

163163163

180°

0°

– 180°

FREQUENCY : f (Hz)

PHASE

Characteristics when using standard
components and standard constants

Fig. 3 Microphone amplifier

frequency characteristics

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Multimedia ICs BA7760 / BA7760F

Output from these dual amplifiers is level-adjusted with
an attached volume control (VR) and then input to pin
7 and mixed by the mixer buffer amplifier. The ON /
OFF operation of the mixer buffer amplifier can be con­trolled with the signal input to pin 13 (MUTE CTRL).
For DC loads, this volume control (VR) should be set
above 4.5kΩ to assure proper performance of the IC’s
internal driver.

Mode Control signal Operation
MUTE L Muted
MUTE H Normal operation

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Application example

Fig. 4

8

9

10

11

12

13

14

7

6

5

4

3

2

1

+

–

+

–

10kΩ

10µF

MIXOUT

(VR)

1µF

220Ω

47µF

150pF

12kΩ

4.7µF

2.2kΩ

MICINMUTE

CTRL

22µF

2.2kΩ

MICIN

(VR)

1µF

220Ω

47µF

150pF

R3

12kΩ

5kΩ

5kΩ

22kΩ

0.1µF

22kΩ

0.1µF

R4

4.7µF

R7

R6

+

–

MIC AMP Ch2

MIC AMP Ch1

MIX BF

Ch2

Ch1

BA7760 / F

VCC

+

+

+

+

+

+

+

+

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Multimedia ICs BA7760 / BA7760F

DIP14 SOP14

BA7760 BA7760F

6.5 ± 0.3

19.4 ± 0.3

0.5 ± 0.1

3.2 ± 0.2 4.25 ± 0.3

14 8

71

0.3 ± 0.1

0.51Min.

7.62

0° ~ 15°

2.54

0.4 ± 0.11.27

1

14

8.7 ± 0.2

7

8

4.4 ± 0.2

6.2 ± 0.3

0.11

1.5 ± 0.1

0.15

0.15 ± 0.1

0.3Min.

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External dimensions (Units: mm)