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LM386M(LM386M).pdf
January 2000
LM386
Low Voltage Audio Power Amplifier
Features
General Description
n Battery operation
The LM386 is a power amplifier designed for use in low volt-
age consumer applications. The gain is internally set to 20 to
n Minimum external parts
keep external part count low, but the addition of an external
n Wide supply voltage range:
resistor and capacitor between pins 1 and 8 will increase the
n Low quiescent current drain: 4 mA
gain to any value up to 200.
n Voltage gains from 20 to 200
The inputs are ground referenced while the output is auto-
n Ground referenced input
matically biased to one half the supply voltage. The quies-
n Self-centering output quiescent voltage
cent power drain is only 24 milliwatts when operating from a
n Low distortion
6 volt supply, making the LM386 ideal for battery operation.
n Available in 8 pin MSOP package
4V–12V or 5V–18V
Applications
n AM-FM radio amplifiers
n Portable tape player amplifiers
n Intercoms
n TV sound systems
n Line drivers
n Ultrasonic drivers
n Small servo drivers
n Power converters
Equivalent Schematic and Connection Diagrams
Small Outline,
Molded Mini Small Outline,
and Dual-In-Line Packages
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P
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DS006976-1
DS006976-2
Top View
Order Number LM386M-1,
LM386MM-1, LM386N-1,
LM386N-3 or LM386N-4
See NS Package Number
M08A, MUA08A or N08E
© 2000 National Semiconductor Corporation
DS006976
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Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
(LM386N-1, -3, LM386M-1)
Supply Voltage (LM386N-4)
Package Dissipation (Note 3)
(LM386N)
(LM386M)
(LM386MM-1)
Input Voltage
Storage Temperature
Operating Temperature
Junction Temperature
Soldering Information
15V
22V
1.25W
0.73W
0.595W
±0.4V
−65˚C to +150˚C
0˚C to +70˚C
+150˚C
Electrical Characteristics (Notes 1, 2)
TA = 25˚C
Dual-In-Line Package
Soldering (10 sec)
Small Outline Package
(SOIC and MSOP)
Vapor Phase (60 sec)
Infrared (15 sec)
+260˚C
+215˚C
+220˚C
See AN-450 “Surface Mounting Methods and Their Effect
on Product Reliability” for other methods of soldering
surface mount devices.
Thermal Resistance
q JC (DIP)
q JA (DIP)
q JC (SO Package)
q JA (SO Package)
q JA (MSOP)
q JC (MSOP)
37˚C/W
107˚C/W
35˚C/W
172˚C/W
210˚C/W
56˚C/W
Parameter
Conditions
Min
Typ
Max
Units
Operating Supply Voltage (VS)
LM386N-1, -3, LM386M-1, LM386MM-1
LM386N-4
Quiescent Current (IQ)
Output Power (POUT)
LM386N-1, LM386M-1, LM386MM-1
LM386N-3
LM386N-4
Voltage Gain (AV)
Bandwidth (BW)
Total Harmonic Distortion (THD)
Power Supply Rejection Ratio (PSRR)
VS = 6V, VIN = 0
, THD = 10%
, THD = 10%
, THD = 10%
VS = 6V, RL = 8W
VS = 9V, RL = 8W
VS = 16V, RL = 32W
VS = 6V, f = 1 kHz
10 µF from Pin 1 to 8
VS = 6V, Pins 1 and 8 Open
VS = 6V, RL = 8W
f = 1 kHz, Pins 1 and 8 Open
VS = 6V, f = 1 kHz, CBYPASS = 10 µF
Pins 1 and 8 Open, Referred to Output
, POUT = 125 mW
Input Resistance (RIN)
Input Bias Current (IBIAS)
VS = 6V, Pins 2 and 3 Open
12
18
8
4
5
250
500
700
4
325
700
1000
26
46
300
0.2
50
50
250
V
V
mA
mW
mW
mW
dB
dB
kHz
%
dB
kW
nA
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is func-
tional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guar-
antee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is
given, however, the typical value is a good indication of device performance.
Note 3: For operation in ambient temperatures above 25˚C, the device must be derated based on a 150˚C maximum junction temperature and 1) a thermal resis-
tance of 107˚C/W junction to ambient for the dual-in-line package and 2) a thermal resistance of 170˚C/W for the small outline package.
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Application Hints
GAIN CONTROL
To make the LM386 a more versatile amplifier, two pins (1
and 8) are provided for gain control. With pins 1 and 8 open
the 1.35 kW
resistor sets the gain at 20 (26 dB). If a capacitor
is put from pin 1 to 8, bypassing the 1.35 kW
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. Gain control can also be done by capacitively cou-
pling a resistor (or FET) from pin 1 to ground.
Additional external components can be placed in parallel
with the internal feedback resistors to tailor the gain and fre-
quency 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 series
RC from pin 1 to 5 (paralleling the internal 15 kW
resistor).
For 6 dB effective bass boost: R @ 15 kW
, the lowest value
for good stable operation is R = 10 kW
if pin 8 is open. If pins
1 and 8 are bypassed then R as low as 2 kW
can be used.
This restriction is because the amplifier is only compensated
for closed-loop gains greater than 9.
INPUT BIASING
The schematic shows that both inputs are biased to ground
with a 50 kW
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 LM386
is higher than 250 kW
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 kW
, 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 put-
ting a resistor from the unused input to ground, equal
in
value to the dc source resistance. Of course all offset prob-
lems are eliminated if the input is capacitively coupled.
When using the LM386 with higher gains (bypassing the
1.35 kW
resistor between pins 1 and 8) it is necessary to by-
pass the unused input, preventing degradation of gain and
possible instabilities. This is done with a 0.1 µF capacitor or
a short to ground depending on the dc source resistance on
the driven input.
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Typical Performance Characteristics
Quiescent Supply Current
vs Supply Voltage
Power Supply Rejection Ratio
(Referred to the Output)
vs Frequency
Peak-to-Peak Output Voltage
Swing vs Supply Voltage
DS006976-5
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DS006976-13
Voltage Gain vs Frequency
Distortion vs Frequency
Distortion vs Output Power
DS006976-14
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Device Dissipation vs Output
Power — 4W Load
Device Dissipation vs Output
Power — 8W Load
Device Dissipation vs Output
Power — 16W Load
DS006976-17
DS006976-18
DS006976-19
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Typical Applications
Amplifier with Gain = 20
Minimum Parts
Amplifier with Gain = 200
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Amplifier with Gain = 50
Low Distortion Power Wienbridge Oscillator
DS006976-6
Amplifier with Bass Boost
Square Wave Oscillator
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DS006976-9
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Typical Applications (Continued)
Frequency Response with Bass Boost
DS006976-10
AM Radio Power Amplifier
Note 4: Twist Supply lead and supply ground very tightly.
Note 5: Twist speaker lead and ground very tightly.
Note 6: Ferrite bead in Ferroxcube K5-001-001/3B with 3 turns of wire.
Note 7: R1C1 band limits input signals.
Note 8: All components must be spaced very closely to IC.
DS006976-11
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Physical Dimensions inches (millimeters) unless otherwise noted
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SO Package (M)
Order Number LM386M-1
NS Package Number M08A
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Lead (0.118” Wide) Molded Mini Small Outline Package
Order Number LM386MM-1
NS Package Number MUA08A
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