LM386
LM386 Low Voltage Audio Power Amplifier
Literature Number: SNAS545A
LM386
Low Voltage Audio Power Amplifier
General Description
The LM386 is a power amplifier designed for use in low volt-
age consumer applications. The gain is internally set to 20 to
keep external part count low, but the addition of an external
resistor and capacitor between pins 1 and 8 will increase the
gain to any value from 20 to 200.
The inputs are ground referenced while the output automati-
cally biases to one-half the supply voltage. The quiescent
power drain is only 24 milliwatts when operating from a 6 volt
supply, making the LM386 ideal for battery operation.
Features
nBattery operation
nMinimum external parts
nWide supply voltage range: 4V–12V or 5V–18V
nLow quiescent current drain: 4mA
nVoltage gains from 20 to 200
nGround referenced input
nSelf-centering output quiescent voltage
nLow distortion: 0.2% (A
V
= 20, V
S
=6V,R
L
=8Ω,P
O
=
125mW, f = 1kHz)
nAvailable in 8 pin MSOP package
Applications
nAM-FM radio amplifiers
nPortable tape player amplifiers
nIntercoms
nTV sound systems
nLine drivers
nUltrasonic drivers
nSmall servo drivers
nPower converters
Equivalent Schematic and Connection Diagrams
DS006976-1
Small Outline,
Molded Mini Small Outline,
and Dual-In-Line Packages
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
August 2000
LM386 Low Voltage Audio Power Amplifier
© 2000 National Semiconductor Corporation DS006976 www.national.com
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) 15V
Supply Voltage (LM386N-4) 22V
Package Dissipation (Note 3)
(LM386N) 1.25W
(LM386M) 0.73W
(LM386MM-1) 0.595W
Input Voltage ±0.4V
Storage Temperature −65˚C to +150˚C
Operating Temperature 0˚C to +70˚C
Junction Temperature +150˚C
Soldering Information
Dual-In-Line Package
Soldering (10 sec) +260˚C
Small Outline Package
(SOIC and MSOP)
Vapor Phase (60 sec) +215˚C
Infrared (15 sec) +220˚C
See AN-450 “Surface Mounting Methods and Their Effect
on Product Reliability” for other methods of soldering
surface mount devices.
Thermal Resistance
θ
JC
(DIP) 37˚C/W
θ
JA
(DIP) 107˚C/W
θ
JC
(SO Package) 35˚C/W
θ
JA
(SO Package) 172˚C/W
θ
JA
(MSOP) 210˚C/W
θ
JC
(MSOP) 56˚C/W
Electrical Characteristics (Notes 1, 2)
T
A
= 25˚C
Parameter Conditions Min Typ Max Units
Operating Supply Voltage (V
S
)
LM386N-1, -3, LM386M-1, LM386MM-1 4 12 V
LM386N-4 518V
Quiescent Current (I
Q
)V
S
= 6V, V
IN
=0 4 8 mA
Output Power (P
OUT
)
LM386N-1, LM386M-1, LM386MM-1 V
S
= 6V, R
L
=8Ω, THD = 10% 250 325 mW
LM386N-3 V
S
= 9V, R
L
=8Ω, THD = 10% 500 700 mW
LM386N-4 V
S
= 16V, R
L
=32Ω, THD = 10% 700 1000 mW
Voltage Gain (A
V
)V
S
= 6V, f = 1 kHz 26 dB
10 µF from Pin 1 to 8 46 dB
Bandwidth (BW) V
S
= 6V, Pins 1 and 8 Open 300 kHz
Total Harmonic Distortion (THD) V
S
= 6V, R
L
=8Ω,P
OUT
= 125 mW 0.2 %
f = 1 kHz, Pins 1 and 8 Open
Power Supply Rejection Ratio (PSRR) V
S
= 6V, f = 1 kHz, C
BYPASS
=10µF 50 dB
Pins 1 and 8 Open, Referred to Output
Input Resistance (R
IN
) 50 kΩ
Input Bias Current (I
BIAS
)V
S
= 6V, Pins 2 and 3 Open 250 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 andAC 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.
LM386
www.national.com 2
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 kΩresistor sets the gain at 20 (26 dB). If a capacitor
is put from pin 1 to 8, bypassing the 1.35 kΩresistor, 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 kΩresistor).
For 6 dB effective bass boost: R .15 kΩ, the lowest value
for good stable operation is R = 10 kΩif pin 8 is open. If pins
1 and 8 are bypassed then R as low as 2 kΩcan 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
witha50kΩresistor. 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 kΩit 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 kΩ, 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 kΩresistor 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.
LM386
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Typical Performance Characteristics
Quiescent Supply Current
vs Supply Voltage
DS006976-5
Power Supply Rejection Ratio
(Referred to the Output)
vs Frequency
DS006976-12
Peak-to-Peak Output Voltage
Swing vs Supply Voltage
DS006976-13
Voltage Gain vs Frequency
DS006976-14
Distortion vs Frequency
DS006976-15
Distortion vs Output Power
DS006976-16
Device Dissipation vs Output
Power—4ΩLoad
DS006976-17
Device Dissipation vs Output
Power—8ΩLoad
DS006976-18
Device Dissipation vs Output
Power—16ΩLoad
DS006976-19
LM386
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Typical Applications
Amplifier with Gain = 20
Minimum Parts
DS006976-3
Amplifier with Gain = 200
DS006976-4
Amplifier with Gain = 50
DS006976-6
Low Distortion Power Wienbridge Oscillator
DS006976-7
Amplifier with Bass Boost
DS006976-8
Square Wave Oscillator
DS006976-9
LM386
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Typical Applications (Continued)
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.
Frequency Response with Bass Boost
DS006976-10
AM Radio Power Amplifier
DS006976-11
LM386
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Physical Dimensions inches (millimeters) unless otherwise noted
SO Package (M)
Order Number LM386M-1
NS Package Number M08A
LM386
www.national.com7
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
LM386
www.national.com 8
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury 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
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Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
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Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
Dual-In-Line Package (N)
Order Number LM386N-1, LM386N-3 or LM386N-4
NS Package Number N08E
LM386 Low Voltage Audio Power Amplifier
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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