LM390N [NSC]
LM390 1W Battery Operated Audio Power Amplifier; LM390 1W电池供电音频功率放大器
| 型号： | LM390N |
| 厂家： | 
National Semiconductor |
| 描述： | LM390 1W Battery Operated Audio Power Amplifier |
| 文件： | 总6页 (文件大小：165K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
April 1995
LM390 1W Battery Operated Audio Power Amplifier
Y
Self-centering output quiescent voltage
General Description
The LM390 Power Audio Amplifier is optimized for 6V, 7.5V,
9V operation into low impedance loads. The gain is internal-
ly set at 20 to keep the external part count low, but the
addition of an external resistor and capacitor between pins
2 and 6 wil increase the gain to any value up to 200. The
Y
Variable voltage gain
Y
Low distortion
Y
Fourteen pin dual-in-line package
Applications
Y
AM-FM radio amplifiers
Portable tape player amplifiers
Intercoms
inputs are ground referenced while the output is automati-
cally biased to one half the supply voltage.
Y
Y
Y
Y
Y
Y
Y
Y
Features
Y
TV sound systems
Lamp drivers
Battery operation
Y
1W output power
Line drivers
Y
Minimum external parts
Ultrasonic drivers
Small servo drivers
Power converters
Y
Excellent supply rejection
Y
Ground referenced input
Equivalent Schematic and Connection Diagrams
Dual-In-Line Package
TL/H/7848–2
Order Number LM390N
See NS Package Number N14A
TL/H/7848–1
C
1995 National Semiconductor Corporation
TL/H/7848
RRD-B30M115/Printed in U. S. A.
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
a
0 C to 70 C
Operating Temperature
§
§
Junction Temperature
150 C
§
Lead Temperature (Soldering, 10 sec.)
Thermal Resistance
260 C
§
Supply Voltage
10V
Package Dissipation 14-Pin DIP (Note 1)
Input Voltage
8.3W
i
i
30 C/W
§
JC
g
0.4V
79 C/W
§
JA
b
a
65 C to 150 C
Storage Temperature
§
§
e
Electrical Characteristics T
25 C,(Figure 1)
§
A
Symbol
Parameter
Operating Supply Voltage
Quiescent Current
Output Power
Conditions
Min
Typ
Max
9
Units
V
V
S
4
e
e
e
e
I
V
6V, V
IN
0
10
20
mA
W
Q
S
S
S
e
L
e
P
V
6V, R
4X, THD
10%
0.8
23
1.0
OUT
e
A
V
Voltage Gain
V
6V, f
1 kHz
26
46
30
1
dB
dB
10 mF from Pin 2 to 6
e
e
e
BW
Bandwidth
V
S
6V, Pins 2 and 6 Open
300
0.2
kHz
%
e
e
500 mW
THD
Total Harmonic Distortion
V
S
6V, R
4X, P
L
OUT
f
1 kHz, Pins 2 and 6 Open
e
e
e
1 kHz, C 10 mF,
BYPASS
PSRR
Power Supply Rejection Ratio
V
S
6V, f
Pins 2 and 6 Open, Referred to Output
(Note 2)
50
dB
R
Input Resistance
Input Bias Current
10
50
kX
IN
e
V
S
I
6V, Pins 7 and 8 Open
250
nA
BIAS
Note 1: Pins 3, 4, 5, 10, 11, 12 at 25 C. Above 25 C case, derate at 15 C/W junction to case, or 85 C/W junction to ambient.
§
§
§
Note 2: If load and bypass capacitor are returned to V (Figure 2), rather than ground (Figure 1), PSRR is typically 30 dB.
§
S
Typical Performance Characteristics
Power Supply Rejection Ratio
(Referred to the Output) vs
Frequency
Maximum Device Dissipation
vs Ambient Temperature
Quiescent Supply Current vs
Supply Voltage
TL/H/7848–5
2
Typical Performance Characteristics (Continued)
Device Dissipation vs
Output Power 4X Load
Device Dissipation vs
Output Power 8X Load
Distortion vs Output Power
TL/H/7848–6
Application Hints
Gain Control
bypass the unused input, preventing degradation of gain
and possible instabilities. This is done with a 0.1 mF capaci-
tor or a short to ground depending on the dc source resist-
ance on the driven input.
To make the LM390 a more versatile amplifier, two pins (2
and 6) are provided for gain control. With pins 2 and 6 open,
the 1.35 kX resistor sets the gain at 20 (26 dB). If a capaci-
tor is put from pin 2 to 6, bypassing the 1.35 kX resistor, the
gain will go up to 200 (46 dB). If a resistor is placed in series
with the capacitor, the gain can be set to any value from 20
to 200. A low frequency pole in the gain response is caused
by the capacitor working against the external resistor in se-
ries with the 150X internal resistor. If the capacitor is elimi-
nated and a resistor connects pin 2 to 6 then the output dc
level may shift due to the additional dc gain. Gain control
can also be done by capacitively coupling a resistor (or
FET) from pin 6 to ground, as in Figure 7.
Bootstrapping
The base of the output transistor of the LM390 is brought
out to pin 9 for Bootstrapping. The output stage of the am-
plifier during positive swing is shown in Figure 3 with its
external circuitry.
a
R1
R2 set the amount of base current available to the
output transistor. The maximum output current divided by
beta is the value required for the current in R1 and R2:
b
(V /2)
S
V
BE
a
e
b
(R1
R2)
O
Additional external components can be placed in parallel
with the internal feedback resistors to tailor the gain and
frequency response for individual applications. For example,
we can compensate poor speaker bass response by fre-
quency shaping the feedback path. This is done with a se-
ries RC from pin 6 to 13 (paralleling the internal 15 kX resis-
I
O MAX
e
e
100.
Good design values are V
0.7V and b
BE
O
e
Example 0.8 watt into 4X load with V
6V.
S
2 P
R
O
e
e
632 mA
I
O MAX
0
L
j
e
tor). For 6 dB effective bass boost: R
value for good stable operation is R
15 kX, the lowest
10 kX if pin 2 is
b
(6/2) 0.7
0.632
a
e
e
364X
(R1
R2)
100
#
J
open. If pins 2 and 6 are bypassed then R as low as 2 kX
can be used. This restriction is because the amplifier is only
compensated for closed-loop gains greater than 9 V/V.
To keep the current in R2 constant during positive swing
capacitor C is added. As the output swings positive C lifts
B
B
R1 and R2 above the supply, maintaining a constant voltage
e
Input Biasing
across R2. To minimize the value of C , R1
B
R2. The pole
due to C and R1 and R2 is usually set equal to the pole
B
The schematic shows that both inputs are biased to ground
with a 50 kX resistor. The base current of the input transis-
tors is about 250 nA, so the inputs are at about 12.5 mV
when left open. If the dc source resistance driving the
LM390 is higher than 250 kX it will contribute very little
additional offset (about 2.5 mV at the input, 50 mV at the
output). If the dc source resistance is less than 10 kX, then
shorting the unused input to ground will keep the offset low
(about 2.5 mV at the input 50 mV at the output). For dc
source resistances between these values we can eliminate
excess offset by putting a resistor from the unused input to
ground, equal in value to the dc source resistance. Of
course all offset problems are eliminated if the input is ca-
pacitively coupled.
due to the output coupling capacitor and the load. This
gives:
4C
C
c
c
j
j
C
B
b
25
O
e
e
c
Example: for 100 Hz pole and R
e
4X; C
400 mF and
L
C
16 mF, if R1 is made a diode and R2 increased to give
B
the same current, C can be decreased by about a factor of
B
4, as in Figure 4.
For reduced component count the load can replace R1. The
a
value of (R1
R2) is the same, so R2 is increased. Now C
B
is both the coupling and the bootstrapping capacitor (see
Figure 2).
When using the LM390 with higher gains (bypassing the
1.35 kX resistor between pins 2 and 6) it is necessary to
3
Typical Applications
TL/H/7848–4
TL/H/7848–3
FIGURE 2. Load Returned to Supply
e
FIGURE 1. Load Returned to Ground
e
(Amplifier with Gain
20)
(Amplifier with Gain
20)
TL/H/7848–7
FIGURE 3
TL/H/7848–8
e
FIGURE 4. Amplifier with Gain
200 and Minimum C
B
TL/H/7848–9
FIGURE 5. 2.5W Bridge Amplifier
4
Typical Applications (Continued)
TL/H/7848–11
FIGURE 6(b). Frequency Response
with Bass Boost
TL/H/7848–10
FIGURE 6(a). Amplifier with Bass Boost
TL/H/7848–12
FIGURE 7. Intercom
TL/H/7848–13
FIGURE 8. AM Radio Power Amplifier
Note 1: Twist supply lead and supply ground very tightly.
Note 4: R1C1 band limits input signals.
Note 5: All components must be spaced very close to IC.
Note 2: Twist speaker lead and ground very tightly.
Note 3: Ferrite bead is Ferroxcube K5-001-001/3B with 3 turns of wire.
5
Physical Dimensions inches (millimeters)
Molded Dual-In-Line Package (N)
Order Number LM390N
See NS Package Number N14A
LIFE SUPPORT POLICY
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with instructions for use provided in the labeling, can
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to the user.
2. A critical component is any component of a life
support device or system whose failure to perform can
be reasonably expected to cause the failure of the life
support device or system, or to affect its safety or
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