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).
•
Applications with karaoke features, VCRs, LDs, etc.
Audio equipment
•
Features2-channel low noise microphone amplifier.
1) Internal
2) Internal mixer buffer amplifier with mute function.
3) Available in 2 types of packages: DIP 14-pin or SOP
14-pin.
•
Absolute maximum ratings (Ta = 25°C)
Parameter
Applied voltage
Power
dissipation
BA7760
BA7760F
Symbol
V
CC
Pd
Topr
Tstg
Limits
15
600
∗
1
450
∗
2
– 25 ~ + 75
– 55 ~ + 125
Unit
V
mW
°C
°C
Operating temperature
Storage temperature
∗
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.
•
Recommended operating conditions
Parameter
Power supply voltage
Symbol
V
CC
Limits
6 ~ 14
Unit
V
1
Multimedia ICs
BA7760 / BA7760F
•
Block diagram
3 MIC IN Ch1 ( + )
1 RIPPLE FILTER
4 MIC IN Ch1 ( – )
6 MIC OUT Ch1
5 FILTER Ch1
7 MIX IN
2 GND
MUTE CTRL 13
–
MIX BF
+
+
–
MIC AMP CH 1
MIC AMP CH 2
+
–
FILTER Ch2 10
MIC IN Ch2 ( – ) 11
MIC IN Ch2 ( + ) 12
MIX OUT 8
•
Pin descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Pin name
RIPPLE FILTER
GND
MIC IN ( + ) Ch1
MIC IN ( – ) Ch1
FILTER Ch1
MIC OUT Ch1
MIX IN
MIX OUT
MIC OUT Ch2
FILTER Ch2
MIC IN ( + ) Ch2
MIC IN ( – ) Ch2
MUTE CTRL
V
CC
Ripple filter
GND
CH1 microphone amplifier input ( + )
CH1 microphone amplifier input ( – )
CH1 microphone amplifier fc
CH1 microphone amplifier output
Mixer buffer input
Mixer buffer output
CH2 microphone amplifier output
CH2 microphone amplifier fc
CH2 microphone amplifier input ( – )
CH2 microphone amplifier input ( + )
Mute control
V
CC
Function
Pin type
Base (NPN) // 15kΩ
—
Base (NPN) // 120kΩ
Base (NPN)
Base (NPN) ~ 450Ω
Push-pull
Base (NPN) // 65kΩ
Push-pull
Push-pull
Base (NPN) ~ 450Ω
Base (NPN)
Base (NPN) // 120kΩ
Fig.1
—
∗
“Parallel” and “series” respectively refer to parallel and series insertion. All figures are standard values.
2
MIC OUT Ch2 9
V
CC
14
Multimedia ICs
BA7760 / BA7760F
•
Input / output circuits
40kΩ
MUTE CTRL 13
Fig. 1
•
Electrical characteristics (unless otherwise noted, Vcc = 12V, Ta = 25°C)
Parameter
Supply current
Symbol
I
q
Min.
3.65
Typ.
4.87
Max.
6.09
Unit
mA
Conditions
—
〈
MIC AMP (G
VC
= 36dB, f = 1kHz)
〉
Open loop voltage gain
Input conversion noise
Distortion
Maximum output level
Input impedance
Crosstalk
G
VOM
V
nM
THD
M
V
omM
Z
inM
CT
M
55.0
—
—
8.3
92
—
65.0
– 122
0.008
10.4
123
– 86
—
– 114
0.1
—
—
– 78
dB
dBV
%
dBV
kΩ
dBV
V
IN
= – 70dBV
Rg = 2.2kΩ, DIN AUDIO
V
IN
= – 40dBV
B.W. = 0.4 ~ 30kHz
THD = 1%
B.W. = 0.4 ~ 30kHz
V
IN
= – 40dBV, 100kΩAttenuation
V
IN
= – 36dBV
R
g
= 2.2kΩ, DIN AUDIO
〈
MIX BF (f = 1kHz)
〉
Voltage gain
Output residual noise
Distortion
Maximum output level
Input impedance
Mute level
Mute threshold voltage
G
VB
V
nB
THD
B
V
OMB
Z
inB
MT
B
V
THMUTE
– 0.7
—
—
8.3
50.0
—
2.12
0
– 110
0.002
10.5
66.5
– 110
2.62
0.7
– 100
0.07
—
—
– 100
3.12
dB
dBV
%
dBV
kΩ
dBV
V
V
IN
= – 10dBV
R
g
= 2.2kΩ, DIN AUDIO
V
IN
= – 10dBV
B.W. = 0.4 ~ 30kHz
THD = 1%
B.W. = 0.4 ~ 30kHz
V
IN
= – 10dBV, 50kΩAttenuation
V
IN
= – 10dBV, DIN AUDIO
—
3
Multimedia ICs
BA7760 / BA7760F
•
Measurement circuit
MIX OUT
10kΩ
MIX BF
8
5kΩ
10µF
+
–
9
150pF
6
150pF
7
+
4.7µF
5kΩ
2.2kΩ
MIX IN
1MΩ
470µF
+
11
+
47µF
MIC IN
Ch2
220Ω
4.7µF
4
220Ω
+
47µF
MIC IN
Ch1
MIC OUT
Ch2
MIC OUT
Ch1
2.2kΩ
13
2
22µF
13.9kΩ
MIC AMP Ch2
10
MIC AMP Ch1
13.9kΩ
1MΩ
–
+
+
–
5
470µF
+
+
4.7µF
2.2kΩ
12
3
+
MUTE
CTRL
V
CC
14
1
+
BA7760 / F
Fig. 2
(Refer to “Application Example”)
•
Circuit operationBA7760F are dual microphone ampli-
The BA7760 and
VOLTAGE GAIN : G
V
(dB)
fiers. 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
C
C
20dB
=
15
0p
F
0dB
180°
0°
3 61 3 61 3 61 3 61 3 61
– 180°
1kHz 10kHz 100kHz 1MHz 10MHz 100MHz
FREQUENCY : f (Hz)
Characteristics when using standard
components and standard constants
– 20dB
Fig. 3 Microphone amplifier
frequency characteristics
4
PHASE
=
0
Multimedia ICs
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 con-
trolled 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
MUTE
MUTE
BA7760 / BA7760F
Control signal
L
H
Operation
Muted
Normal operation
•
Application example
MIXOUT
MIX BF
+
10µF
9
150pF
MIC AMP Ch2
MIC AMP Ch1
6
150pF
5kΩ
(VR)
1µF
12kΩ
1µF
12kΩ
R6
–
+
+
–
R7
11
220Ω
4
47µF
+
R3
10
5
R4
+
220Ω
4.7µF
+
+
MICIN
Ch2
22kΩ
+
–
5kΩ
(VR)
47µF
MICIN
Ch1
12
3
4.7µF
2.2kΩ
MUTE
CTRL
13
2
2.2kΩ
V
CC
14
1
22µF
BA7760 / F
Fig. 4
0.1µF
8
+
7
0.1µF
10kΩ
22kΩ
+
+
5
Power technology
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