NJM2781
– 1 –
Monaural Microphone Amplifier
■ GENERAL DESCRIPTION
The NJM2781 is a monaural microphone amplifier IC with a
standby function, and can vary a voltage gain by adjusting an
external resistor.
Since the NJM2781 operates with a low voltage range of +2.7V to
+4.5V and is available in tiny packages of MSOP8(TVSP8)* and
SSOP8, it is ideally suited for portable and handheld components.
■ FEATURES
● Operating Voltage +2.7V to +4.5 V
● Operating Current 1.8mA typ.
1µA max. (in Standby mode)
● Bipolar Technology
● Package Outline MSOP8(TVSP8) *
SSOP8
*MEET JEDEC MO-187-DA / THIN TYPE
■ BLOCK DIAGRAM
■ PIN FUNCTION
■PACKAGE OUTLINE
1
4 5
8
No. SYMBOL FUNCTION No. SYMBOL FUNCTION
1 NOISE Noise Bypass 5 IN- Inverted Input
2 REG Regulator Output 6 OUT Output
3 STBY Standby On/Off 7 V+ Power Supply
4 IN+ Non-Inverted Input 8 GND Ground
4
3
2
1 8
7
6
5
Reg
GND
V+
OUT
IN-
NOISE
REG
IN+
STBY
NJM2781RB1
MSOP8(TVSP8)
NJM2781
V
( SSOP8 )
NJM2781
– 2 –
■ ABSOLUTE MAXIMUM RATING (Ta=25°
°°
°C)
PARAMETER SYMBOL RATING UNIT
Supply Voltage V
+
5 V
Power Dissipation P
D
MSOP8(TVSP8):320, SSOP8:250 mW
Operating Temperature Range Topr -40 to 85 °C
Storage Temperature Range Tstg -40 to 125 °C
■ ELECTRICAL CHARACTERISTICS
(Ta=25°C,V
+
=2.8V,Vin=-40dBV, f=1kHz,R
L
=9kΩ)
●Power Supply
PARAMETER SYMBOL TEST CONDITION MIN. TYP. MAX. UNIT
Operating Voltage V
+
2.7 2.8 4.5 V
Operating Current 1 Icc1 No signal, Standby - 1 µA
Operating Current 2 Icc2 No signal, Active 1.8 4 mA
Mic Power Supply Voltage Vo RL=6.8kΩ 2.3 2.42 2.54 V
● Amplifier
PARAMETER SYMBOL TEST CONDITION MIN. TYP. MAX. UNIT
Output Voltage Vo 1.28 1.35 1.42 V
Voltage Gain G
V
Test Circuit 1 24 25 26 dB
Maximum Output Voltage V
OM
THD=0.1% -2.7
(0.73)
-1.5
(0.84) - dBV
(Vrms)
Total Harmonic Distortion
(THD+N) THD - 0.025 0.1 %
Output Noise V
NO
Rg=600Ω, A-Weighted - -98
(12.6)
-90
(31.6)
dBV
(µVrms)
Power Supply Ripple
Rejection PSRR Rg=600Ω,
Vripple=-20dBV 65 80 - dB
●Control
PARAMETER SYMBOL TEST CONDITION MIN. TYP. MAX. UNIT
High Level Input Voltage V
IH
STBY terminal 2 - V
+
V
Low Level Input Voltage V
IL
STBY terminal 0 - 0.5 V
■
Standby Mode Operation
Control Terminal
Status
STBY
IC Condition
Active H IC active
Standby L, OPEN IC standby
NJM2781
– 3 –
■ TEST CIRCUIT
Test Circuit 1 (
Voltage Gain
Gv,
Maximum Output Voltage
V
OM
,
Total Harmonic Distortion
THD)
Test Circuit 2 (
DC Output Voltage
V
O
,
Output Noise
V
NO
)
1µF
10µF
10µF
6.8kΩ
0.33µF
2.2µF
9kΩ
4.7µF
Input
Output
V+
GND
[THD]
BPF:400 to 22kHz
15kΩ
680Ω
47kΩ
100Ω
V+
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
V+
GND
Rg=600Ω
2.2µF
9kΩ
4.7µF
Output
[V
NO
]
A
-Weighted
15kΩ
680Ω
47kΩ
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
1µF
10µF
10µF
6.8kΩ
0.33µF
Inpu
t
100Ω
V+
NJM2781
– 4 –
Test Circuit 3 (
Operating Current
Icc1,Icc2)
Test Circuit 4 (
Mic Power Supply Voltage
Vo)
1µF
10µF
6.8kΩ
0.33µF
Input
V+
GND
6.8kΩ
2.2µF
9kΩ
4.7µF
Output
15kΩ
680Ω
47kΩ
100Ω
V+
V+
GND
2.2µF
9kΩ
4.7µF
Output
15kΩ
680Ω
47kΩ
Icc1:STBY=L
Icc2:STBY=H
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
1µF
10µF
10µF
6.8kΩ
0.33µF
Inpu
t
100Ω
V+
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
10µF
NJM2781
– 5 –
Test Circuit 5 (
Power Supply Ripple Rejection
PSRR)
Test Circuit 6 (
Stand-By Control Voltage
V
IH
, V
IL
)
V+
GND
2.2µF
9kΩ
4.7µF
Output
[PSRR]
BPF:1kHz
15kΩ
680Ω
47kΩ
1µF
10µF
10µF
6.8kΩ
0.33µF
2.2µF
9kΩ
4.7µF
Input
Output
V+
GND
15kΩ
680Ω
47kΩ
100Ω
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
Rg=600Ω
1µF
10µF
10µF
6.8kΩ
0.33µF
Inpu
t
100Ω
V+
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
NJM2781
– 6 –
■ APPLICATION CIRCUIT
V+
GND
2.2µF
9kΩ
4.7µF
Output
15kΩ
680Ω
47kΩ
4
3
2
1 8
7
6
5
Reg
NOISE
REG
STBY
IN+
GND
V+
OUT
IN-
1µF
10µF
10µF
6.8kΩ
0.33µF
Inpu
t
100Ω
V+
NJM2781
– 7 –
■ TERMINAL DESCRIPTION
PIN
NO.
SYMBOL FUNCTION EQUIVALENT CIRCUIT
TERMINAL
VOLTAGE
1 NOISE Noise Bypass
0.54V
2 REG Regulator Output
2.42V
3 STBY Standby On/Off
0V
4 IN+ Non-Inverted Input
1.35V
V
+
V
+
V
+
V
+
NOISE
500
3.6
k
27
k
V
+
V
+
V
+
REG
8
k
V
+
460
STB
Y
V
+
30k
30k
V
+
REG
IN+
48k
76k 60k
NJM2781
– 8 –
■ TERMINAL DESCRIPTION
PIN
NO.
SYMBOL FUNCTION EQUIVALENT CIRCUIT
TERMINAL
VOLTAGE
5 IN- Inverted Input
1.35V
6 OUT Output
1.35V
V
+
IN-
V
+
V
+
OUT
16p
300
NJM2781
– 9 –
■ TYPICAL CHARACTERISTICS
Operating Current vs. Pow er Supply Voltage (Active)
RL=9kΩ,Ta=25°C
-0.5
0
0.5
1
1.5
2
2.5
012345
Pow er Supply Voltage [V]
Operating Current [mA]
Operating Current vs. Ambient Temperature (Active)
V+=2.8V,RL=9kΩ
-0.5
0
0.5
1
1.5
2
2.5
-40 10 60 110
Ambient Temperature [°C]
Operating Current [mA]
Operating Current vs. Pow er Supply Voltage (Standby)
R
L
=9kΩ,Ta=25°C
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
012345
Pow er Supply V oltage [V]
Operating Current [µA]
Operating Current vs. Ambient Temperature (Standby)
V+=2.8V,R
L
=9kΩ
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-40 10 60 110
Ambient Teperature [°C]
Operating Current [µA]
Operating Current vs. Standby Voltage
V+=2.8V,R
L
=9kΩ,Ta=25°C
-0.5
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5 3
Standby Voltage [V]
Operating Current [mA]
Output Voltage vs. Input Voltage (Standby)
f=1kHz,RL=9kΩ,Ta=25°C
-140
-120
-100
-80
-60
-40
-20
0
-40 -30 -20 -10 0
Input Voltage [dBV]
Output Voltage [dBV]
NJM2781
– 10 –
■ TYPICAL CHARACTERISTICS
Mic Pow er Supply Voltage vs. Pow er Supply Voltage
RL=6.8kΩTa=25°C
-0.5
0
0.5
1
1.5
2
2.5
3
01234
Pow er Supply Voltage [V]
Mic Power Supply Voltage [V]
Mic Pow er Supply Voltage vs. Ambient Temperature
V+=2.8V,RL=6.8kΩ
-0.5
0
0.5
1
1.5
2
2.5
3
-40 10 60 110
Ambient Temperature [°C]
Mic Power Supply Voltage [V]
Voltage Gain vs. Ambient Temperature
V+=2.8V,Vin=-40dBV,f=1kHz,R
L=9kΩ
20
22
24
26
28
30
-40 10 60 110
Ambient Temperature [°C]
Voltage Gain [dB]
Output Noise vs. Ambient Temperature
V+=2.8V,R
L
=9kΩ,Rg=600Ω,A-w eighted
-120
-115
-110
-105
-100
-95
-90
-85
-80
-40 10 60 110
Ambient Temperature [°C]
Output Noise [dBV]
Votage Gain vs. Standby Voltage (Ta)
V+=2.8V,Vin=-40dBV,f =1kHz,R
L
=9kΩ
-120
-100
-80
-60
-40
-20
0
20
40
00.511.522.53
Standby Voltage [V]
Voltage Gain [dB]
Ta=-40°C
Ta=25°C
Ta=85°C
Voltage Gain vs. Frequency
V+=2.8V,Vin=-40dBV,RL=9kΩ,Ta=25°C
20
22
24
26
28
30
10E+0 100E+0 1E+3 10E+3 100E+3
Frequency [Hz]
Voltage Gain [dB]
10 100 1k 10k 100k
NJM2781
– 11 –
■ TYPICAL CHARACTERISTICS
[CAUTION]
The specifications on this data book are only
given for information, without any guarantee
as regards either mistakes or omissions. The
application circuits in this data book are
described only to show representative usages
of the product and not intended for the
guarantee or permission of any right including
the industrial rights.
Total Harmonic Distortion vs. Output Voltage (V+)
Vin=-40dBV,R
L
=9kΩ,Ta=25°C
0.001
0.01
0.1
1
10
-35 -25 -15 -5 5
Output Voltage [dBV]
THD+N [
％
]
V+=2.7V
V+=2.8V
V+=4.5V
Total Harmonic Distortion vs. Output Voltage (Ta)
V+=2.8V,f=1kHz,R
L
=9kΩ
0.001
0.01
0.1
1
10
-35 -25 -15 -5 5
Output Voltage [dBV]
THD+N [
％
]
Ta=-40°C
Ta= 25°C
Ta= 85°C
Total Harmonic Distortion vs. Output Voltage ( f )
V+=2.8V,R
L
=9kΩ,Ta=25°C
0.001
0.01
0.1
1
10
-35 -25 -15 -5 5
Output Voltage [dBV]
THD+N [
％
]
f=10kHz
f=100Hz
f=1kHz
f=100Hz : BW= 10-22kHz
f=1kHz : BW=400-22kHz
f=10kHz : BW=400-80kHz
Pow er Supply Ripple Rejection vs. Frequency
V+=2.8V,Vin=-40dBV,R
L
=9kΩ,Ta=25°C
0
20
40
60
80
100
10E+0 100E+0 1E+3 10E+3 100E+3
Frequency [Hz]
PSRR [dB
]
10 100 1k 10k 100k
