NJM2792
– 1 –
Quad Boost Amplifier
■
■■
■ GENERAL DESCRIPTION
The NJM2792 is a quad boost amplifier designed for car
audio system. It expands the frequency characteristics by
high slew rate.
It can swing 14V peak-to-peak output voltage at 9V. It
consists of four channel non-inverting amplifier with the gain
of 8dB.
It is suitable for car audio system and other boost amplifier
system.
■
■■
■ FEATURES
● Operating Voltage (6 to 11V)
● Operating Current (12mA typ. )
● Boost output Function (V
O
=14Vpp:@V
+
=9V)
● Maximum Output Voltage (4.5Vrms typ., @ f=100kHz )
● Supply Voltage Rejection Ratio (50dB typ. )
● Total Harmonic Distortion (0.003% typ. )
● Noise Output Voltage (5µVrms typ. )
● Bipolar Technology
● Package Outline SSOP20
■
■■
■ BLOCK DIAGRAM
■
■■
■PACKAGE OUTLINE
NJM2792V
LIFT
AMP
SIGNAL
AMP
SIGNAL
AMP
SIGNAL
AMP
SIGNAL
AMP
LIFT
AMP
LF-IN
LR-IN
RF-IN
RR-IN
LF-OUT
LR-OUT
RF-OUT
RR-OUT
C
LS
C
LS
NJM2792
– 2 –
■
■■
■PIN CONFIGURATION
No. Symbol Function No Symbol Function
1 L-GND Ground for Left Channel 11 R-GND Ground for Right Channel
2 L-COUT Capacitor for - Level Shift Left Channel 12 R-CIN Capacitor for + Level Shift Right Channel
3 FL-OUT Output for Front Left Channel 13 RR-OUT Output for Rear Right Channel
4 FL-FB - Input for Front Left Channel 14 RR-FB - Input for Rear Right Channel
5 FL-IN + Input for Front Left Channel 15 RR-IN + Input for Rear Right Channel
6 REF Reference Voltage 16 V+ Power Supply
7 FR-IN + Input for Front Right Channel 17 RL-IN + Input for Rear Left Channel
8 FR-FB - Input for Front Right Channel 18 RL-FB - Input for Rear Left Channel
9 FR-OUT Output for Front Right Channel 19 RL-OUT Output for Rear Left Channel
10 R-COUT Capacitor for - Level Shift Right Channel 20 L-CIN Capacitor for + Level Shift Left Channel
2
3
4
5
6
7
8
9
10
1
20
19
18
17
16
L-GND
L-CONT
FL-OUT
REF
FR-IN
FL-FB
FL-IN
FR-FB
FR-OUT
R-COUT
L-CIN
RL-OUT
RL-FB
RR-IN
RR-FB
V+
RR
-
OUT
R-CIN
R-GND
15
14
13
12
11
RL-IN
NJM2792
– 3 –
■ ABSOLUTE MAXIMUM RANGES (Ta=25°C)
PARAMETER SYMBOL RANGE UNIT
Supply Voltage V
+
+15 V
Power Dissipation P
D
550
NOTE: EIA/JEDEC STANDARD Test board (76.2x114.3x1.6mm, 2layer, FR-4) mounting
mW
Operating Temperature Topr -40 to +85 °C
Storage Temperature Tstg -40 to +125 °C
■ ELECTRICAL CHARACTERRISTIC (V
+
=9V,Ta=25°C)
PARAMETER
SYMBOL
TEST CONDITION MIN. TYP. MAX. UNIT
DC CHARACTERRISTIC
Operating Voltage
V
+
6.0 9.0 11.0 V
Operating Current
I
CC
No Signal - 12.0 18.0 mA
Output Voltage
V
ODC
- 7.8 - V
AC CHARACTERRISTI C (f=1kHz , Vo=1Vrms, R
L
=10kΩ)
Voltage Gain
Av
7.5 8.0 8.5 dB
Channel Separation 1
CS1
R
S
=600Ω , V
O
=1Vrms, f = 1kHz,
Front channel vs. Rear channel
70 80 - dB
Channel Separation 2
CS2
R
S
=600Ω , V
O
=1Vrms, f = 1kHz,
L channel vs. R channel
- 100 - dB
Channel Balance
BAL
- - 0.5 dB
Roll-off Low Frequency
f
RL
-1dB - 5 - Hz
Roll-off High Frequency
f
RH
-1dB 100 - - kHz
Input Resistance
R
IN
44 60 76 kΩ
Output Resistance
R
OUT
- 2 - Ω
Maximum Output Voltage 1
V
OM1
THD=0.1%, f = 1kHz 5.0 5.2 - Vrms
Maximum Output Voltage 2
V
OM2
THD=1%, f = 100kHz - 4.5 - Vrms
Noise Output Voltage
V
NO
Rs=0Ω , A-Weighting - 5 10 µVrms
THD1
f=1kHz , V
O
=3Vrms, A-Weighting - 0.003 0.01 %
Total Harmonic Distortion
THD2
f=17Hz to 20kHz , V
O
=3Vrms,
A-Weighting - 0.01 - %
SVR1
Rs=0Ω, f=1kHz , V
RP
=100mVrms 55 - - dB
Supply Voltage
Rejection Ratio
SVR2
Rs=0Ω, f=20Hz to 20kHz ,
V
RP
=100mVrms - 50 - dB
NJM2792
– 4 –
TERMINA L DESCRIPTION
PIN
NO. SYMBOL FUNCTION EQUIVALENT CIRCUIT
TERMINAL
DC
VOLTAGE
2
10
L-COUT
R-COUT
Capacitor for - Level Shift Left Channel
Capacitor for - Level Shift Right Channel
(V
+
-1.4)x0.09
[V]
12
20
3
9
13
19
R-CIN
L-CIN
FL-OUT
FR-OUT
RR-OUT
RL-OUT
Capacitor for + Level Shift Right Channel
Capacitor for + Level Shift Left Channel
Output for Front Left Channel
Output for Front Right Channel
Output for Rear Right Channel
Output for Rear Left Channel
V
+
-0.7 [V]
(12,20PIN)
V
+
-1.4 [V]
(3,9,13,19PIN)
4
8
14
18
5
7
15
17
FL-FB
FR-FB
RR-FB
RL-FB
FL-IN
FR-IN
RR-IN
RL-IN
- Input for Front Left Channel
- Input for Front Right Channel
- Input for Rear Right Channel
- Input for Rear Left Channel
+ Input for Front Left Channel
+ Input for Front Right Channel
+ Input for Rear Right Channel
+ Input for Rear Left Channel
(V
+
-1.4)x0.4
[V]
12kΩ
2PIN,
10PIN
2kΩ2kΩ
5PIN,
7PIN,
15PIN,
17PIN
4PIN,
8PIN,
14PIN,
18PIN
300Ω
300Ω
60kΩ
12PIN,
20PIN
3PIN,
9PIN,
13PIN,
19PIN
8.5kΩ8.5kΩ
NJM2792
– 5 –
TERMINA L DESCRIPTION
PIN
NO. SYMBOL FUNCTION EQUIVALENT CIRCUIT
TERMINAL
DC
VOLTAGE
6 REF Reference Voltage
(V
+
-1.4)x0.6
[V]
24kΩ
44kΩ
46kΩ
24kΩ
44kΩ
46kΩ
6PIN
300Ω
300Ω
NJM2792
– 6 –
■
■■
■ A PPLICATION CIRCUIT
L-GND
L-COUT
FL-OUT
FL-FB
FL-IN
FR-IN
REF
FR-FB
FR-OUT
R-COUT
L-CIN
RL-OUT
RL-FB
RL-IN
V+
RR-IN
RR-FB
RR-OUT
R-CIN
R-GND
10µF
22µF22µF
10µF
10µF10µF
22µF22µF
1.5nF
1.5nF
RL=10kΩ
RL=10kΩRL=10kΩ
RL=10kΩ
33kΩ
22kΩ
22kΩ
33kΩ33kΩ
33kΩ
22kΩ
22kΩ
1
2
3
4
5
6
7
8
9
10
11
20
19
18
17
16
15
14
13
12
36kΩ
24kΩ
36kΩ
24kΩ
60kΩ60kΩ
60kΩ60kΩ
44kΩ24kΩ46kΩ
44kΩ24kΩ46kΩ
Lift Amp
Signal Amp Signal Amp
Front-Left Rear-Left
Front-Right Rear-Right
Signal Amp Signal Amp
Lift Amp
+
+
+
+
+
+
+
+
+
+
+
100nF
47µF
22µF
220µF
220µF
CLS
CLS
NJM2792
– 7 –
■
■■
■ APPLICAT ION NO T E
● OPERATING PRINCIPLE
Figure 1 is block diagram of NJM2792. A right channel and a left channel of figure are the same compositions.
Only the reference voltage terminal and the power-supply voltage terminal are common between channels. One
channel is composed of two signal amplifiers, one lift amplifier, the reference voltage, and the bias.
The signal amplifier is non-reverting amplifier which gain(+8dB) is set by external resistances. However, to
achieve the function of the boost, the output bias point is set near V
+
[=V
+
-1.4]. And, the power-supply voltage of
the signal amplifier is supplied from the lift amplifier output.
The lift amplifier lifts the power-supply voltage of the signal amplifier more than V
+
by the charge pump
mechanism. However, unlike a charge pump, the lift amplifier lifts up voltage only when an input signal swings
above center. The output bias point of the lift amplifier is set near GND[=(V
+
-1.4)*0.09]. When the input signal
swings below center, the power supply of the signal amplifier is supplied from V
+
through the diode.
Figure 2 shows the signal operation and the voltage. V
+
/CIN/OUT/COUT shows terminal voltage. The
NJM2792 can output more than the power-supply voltage when power-supply voltage of the signal amplifier (CIN)
is more than the output voltage.
The NJM2792 does not have standby function and mute function. The stability operation is after the capacitor
of the reference voltage terminal is charged at power supply on.
C1
C
REF
Ci
RL
R2
RL
R1
RL
Co
RL
C
LS-L
Ci
FL
Co
FL
R1
FL
R2
FL
+
+
+
+
+
+
60k 60k
REF
L-GND
V+
46k
24k44k
RL-IN
RL-FB
RL-OUT
L-CIN
Front-Left Rear-Left
Signal Amp
Signal Amp
24k
36k
FL-IN
FL-FB
FL-OUT
L-COUT
1
2
3
4
5
6
20
19
18
17
16
Lift Amp
C2
Input
Output
Bias
Co
RR
C
LS-R
Ci
RR
R1
RR
R2
RR
R1
FR
R2
FR
Co
FR
+
+
+
+
+
60k 60k
FR-IN
R-GND
R-CIN
RR-OUT
RR-FB
RR-IN
R-COUT
FR-OUT
FR-FB
Lift Amp
36k
24k
Signal AmpSignal Amp
Rear-Right
Front-Right
7
8
9
10
11
15
14
13
12
46k24k44k
C3
Bias
Ci
FR
1.5nF
1.5nF
22µF
33k
22k22k
33k
22µF
10µF10µF
220µF
220µF
10µF
22µF22µF
10µF
22k
33k 33k
22k
47µF100nF
Input
Output
Input
Output
Input
Output
V+
OUT
CIN
COUT
time
Voltage
Figure 1: Block diagram and application circuit
Figure 2: Signal operation
NJM2792
– 8 –
● OPERATING PRECAUTIONS
1. External parts
1.1 Bypass capacitor for power supply
Bypass capacitor (C1) for the power supply should use the capacitor of wide temperature range and
high-frequency characteristic. Connect the capacitor near the IC for low interconnection resistance.
1.2 Feedback resister
Set the gain to 8dB with feedback resister R1 and R2 of each channel. The use of high-value resisters
causes increase of the output noise voltage. However, R1+R2 cannot use low-value resisters because of the
load resistance of the signal amplifier. The resistances of the example of application circuit are the recommend
value.
1.3 Input coupling capacitor
The low frequency of the input signal is cut with the high-pass filter that composes of input coupling capacitor
and input impedance (about 60kΩ). The cut-off frequency at capacitor value (10uF) of application circuit is
about 0.3Hz.
1.4 Output coupling capacitor
The low frequency of the output signal is cut with the high-pass filter that composes of output coupling
capacitor (Co) and load resistance. The cut-off frequency lowers when the large capacitor value (Co). When the
load resistance is 10kΩ, the cut-off frequency of application circuit is about 0.8Hz.
1.5 Bypass capacitor for reference voltage
The bypass capacitor (C
REF
) for the reference voltage influences the turn-on time and SVR. When C
REF
is
large, SVR is improved, but turn on time becomes long.
1.6 Boost capacitor
When the boost capacitor (C
Lift
) is large, the distortion of the low frequency decreases.
1.7 Bypass capacitor for CIN terminal
Bypass capacitor (C2/C3) of the CIN terminal absorbs fluctuation of the CIN terminal. The capacitances of
the example of application circuit are the recommend value.
2. Load resistance
The NJM2792 is a line amplifier of class-A output. Connect the load resistance 10kΩ or more.
3. Amplifier gain
The amplifier gain of NJM2792 is decided in the ratio of external resistance R1 and R2. The output bias point
of the signal amplifier changes when the gain is changed. The gain setting of +8dB is the recommend value.
4. Low frequency characteristic
The NJM2792 lifts the power-supply voltage of the signal amplifier by the lift amplifier. The electric power from
the power supply is decided depending on external capacity (C
lift
). Therefore, the distortion of low frequency
increases when the electric power is insufficient. Connect capacitor (C
lift
) of a large capacity value for the
distortion decrease of a low frequency.
NJM2792
– 9 –
5. High frequency characteristic
The high frequency characteristic of NJM2792 can output 4.5Vrms(typ.) at 100kHz. However, note a capacitive
load that increases at the high frequency. Set the total load impedance (load capacitance + load resistance) to
10kΩ or more if the flat high-frequency characteristic is necessary.
6. Signal phase to the front/rear channel
Input the in-phase signal to front/ rear channel of NJM2792. The reverse-phase signal input attenuates output
signal amplitude. Input the signal different in only the signal level to front/rear channel.
Output Voltage vs. Phase Difference
V+=9V, THD=0.1%, Ta=25
o
C
0
1
2
3
4
5
6
7
-180 -90 0 90 180
Phase Difference[deg]
Output Voltage[Vrms]
10kHz 1kHz
100Hz
Maximum Output Voltage vs. Frequency
(V+=9[V], THD=1[%], No-Filter, Ta=25
o
C)
0
1
2
3
4
5
6
10000 100000
Frequency [Hz]
Maximum Output Voltage[Vrms]
1000pF 470pF
220pF
0pF
NJM2792
– 10 –
7. Turn on time
The NJM2792 application circuit connects the capacitance of 47uF with the reference voltage terminal. The
signal amplitude is insufficient after turning on of the power supply by capacitor charge. The turn-on time is long
at a large capacity value, and shortens at a small capacity value. Note the SVR characteristic when connecting
small capacity value.
Rise Time vs Reference Voltage Capacity.
Output voltage 90%
0.01
0.1
1
10
1 10 100
Reference Voltage Capacity [uF]
Rise Time [s]
Waveform Rise Time
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-0.2 0.3 0.8 1.3 1.8
Time [ s ]
Voltage [V]
1uF
2.2uF
4.7uF
10uF
22uF
47uF
Power-supply Rejection Ratio vs. Frequency
0
10
20
30
40
50
60
70
80
10 100 1000 10000 100000
Frequency [Hz]
Power-supply Rejection Ratio [dB]
1uF
2.2uF
4.7uF
10uF
22uF
47uF
NJM2792
– 11 –
● 2-CHANNEL ONLY APPLICATION CIRCUIT
Use combination of front-left and front-right or rear-left and rear-right.
The reverse-phase signal input attenuates output signal amplitude. Input the signal different in only the signal
level to front/rear channel.
The application note doesn't guarantee the characteristic.
Give due consideration to characteristic variation of external parts and IC.
C1
C
REF
C
Lif tL
Ci
FL
Co
FL
R1
FL
R2
FL
+
+
+
+
60k 60k
REF
L-GND
V+
46k
24k44k
RL-IN
RL-FB
RL-OU
T
L-CIN
Front-Left Rear-Left
Signal Amp
Signal Amp
24k
36k
FL-IN
FL-FB
FL-OUT
L-COUT
1
2
3
4
5
6
20
19
18
17
16
Lift Amp
C2
Input
Output
Bias
C
Lif tR
R1
FR
R2
FR
Co
FR
+
+
+
60k 60k
FR-IN
R-GND
R-CIN
RR-OU
RR-FB
RR-IN
R-COUT
FR-OUT
FR-FB
Lift Amp
36k
24k
Signal AmpSignal Amp
Rear-Right
Front-Right
7
8
9
10
11
15
14
13
12
46k
24k44k
C3
Bias
Ci
FR
Input
Output
1.5nF
1.5nF
22k
33k
22µF
10µF
220µF
220µF
22µF
10µF
22k
33k
47µF100nF
NJM2792
– 12 –
TYPICAL CHARACTERISTICS
Noise Output Voltage vs. Ambient Temperature
(V
+
=9V, Rs=0Ω, A-Weighting Filter)
0.0
10.0
20.0
30.0
40.0
-40 -20 0 20 40 60 80 100 120 140
Ambient Temperature [
o
C]
Noise Output Voltage [µVrms]
Voltage Gain vs. Frequency
(V+=9V, RL=10kΩ, Vo=1Vrms)
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10 100 1000 10000 100000
Frequency [Hz]
Voltage Gain [dB]
85
o
C
-40
o
C
25
o
C
DC Output Voltage vs. Operating Voltage
(No signal, R
S
=0Ω, R
L
=10kΩ）
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 2 4 6 8 10 12 14 16
Operating Voltage [V]
DC Output Voltage [V]
-40
o
C
25
o
C
85
o
C
DC Output Voltage vs. Ambient Temperrature
(No signal, R
S
=0Ω, R
L
=10kΩ）
0
2
4
6
8
10
12
14
16
-40 -20 0 20 40 60 80 100 120
Ambient Temperature [
o
C]
DC Output Voltage [V]
V
+
=11V
V
+
=9V
V
+
=6V
Operating Current vs. Ambient Temperature
(No signal, R
S
=0Ω, R
L
=10kΩ）
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
-40 -20 0 20 40 60 80 100 120
Ambient Temperature [
o
C]
Operating Current [mA]
V
+
=11V
V
+
=9V
V
+
=6V
Operationg Current vs. Operating Voltage
(No signal, R
S
=0Ω, R
L
=10kΩ）
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 2 4 6 8 10 12 14 16
Operating Voltage [V]
Operating Current [mA]
-40
o
C
85
o
C
25
o
C
NJM2792
– 13 –
TYPICAL CHARACTERISTICS
Maximum Output Voltage vs. Operating Voltage
(R
L
=10kΩ, f=1kHz, THD=0.1%, LPF=80kHz, Ta=25
o
C)
0
1
2
3
4
5
6
7
8
345678910111213
Operating Voltage [V]
Maximum Output Voltage [Vrms]
Maximum Output Voltage vs. R
L
(V
+
=9V, f=1kHz, THD=0.1%, Ta=25
o
C)
0
1
2
3
4
5
6
7
8
01234567891011
R
L
[kΩ]
Maximum Output Voltage [Vrms]
Channel Separation vs. Frequency
(V
+
=9V, Rs=600Ω, R
L
=10kΩ, Ta=25
o
C)
0
20
40
60
80
100
120
140
10 100 1000 10000 100000 1000000
Frequency [Hz]
Channel Separation [dB]
diagonal channel
Ex.) Front-L ch. vs. Rear-R ch.
Left ch. vs. Right ch.
Front ch. vs Rear Ch.
THD+N vs. Output Voltage
(V
+
=9V, R
L
=10kΩ, C
LS
=220µF, LPF=80kHz, Ta=25
o
C)
0.001
0.01
0.1
1
10
0.01 0.1 1 10
Output Voltage [Vrms]
THD+N [%]
10kHz
1kHz
100Hz
THD+N vs. Frequency
(V
+
=9V, R
L
=10kΩ, Vo=3Vrms, LPF=80kHz, Ta=25
o
C)
0.001
0.01
0.1
1
10
10 100 1000 10000 100000
Frequency [Hz]
THD+N [%]
C
LS
=100µF
C
LS
=220µF
C
LS
=470µF
THD+N vs. Frequency
(V
+
=9V, R
L
=10kΩ, C
LS
=220µF, Vo=3Vrms, LPF=80kHz)
0.001
0.01
0.1
1
10
10 100 1000 10000 100000
Frequency [Hz]
THD+N [%]
85
o
C
25
o
C
-40
o
C
NJM2792
– 14 –
TYPICAL CHARACTERISTICS
[CAUTION]
The specifications on this databook are only
given for information , without any guarantee
as regards either mistakes or omissions. The
application circuits in this databook 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.
Supply Voltage Rejection Ratio vs. Frequency
(V
+
=9V, V
RP
=100mVrms, Rs=0Ω, Ta=25
o
C)
0
10
20
30
40
50
60
70
80
10 100 1000 10000 100000 1000000
Frequency [Hz]
SVR [dB]
Mouser Electronics
Authorized Distributor
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