Datasheet LM386 Datasheet (National Semiconductor)

LM386
Low Voltage Audio Power Amplifier

LM386 Low Voltage Audio Power Amplifier

August 2000

General Description

The LM386 is a power amplifier designed for use in low volt­age 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 automati­cally 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

n Battery operation
n Minimum external parts
n Wide supply voltage range: 4V–12V or 5V–18V
n Low quiescent current drain: 4mA
n Voltage gains from 20 to 200
n Ground referenced input
n Self-centering output quiescent voltage
n Low distortion: 0.2% (A

125mW, f = 1kHz)

n Available in 8 pin MSOP package

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

Molded Mini Small Outline,
and Dual-In-Line Packages

= 20, VS=6V,RL=8Ω,PO=

V

Small Outline,

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Top View

DS006976-1

© 2000 National Semiconductor Corporation DS006976 www.national.com

Order Number LM386M-1,

LM386MM-1, LM386N-1,

LM386N-3 or LM386N-4

See NS Package Number

M08A, MUA08A or N08E

Absolute Maximum Ratings (Note 2)

LM386

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
Storage Temperature −65˚C to +150˚C
Operating Temperature 0˚C to +70˚C
Junction Temperature +150˚C
Soldering Information

±

0.4V

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

(DIP) 37˚C/W

θ

JC

(DIP) 107˚C/W

θ

JA

(SO Package) 35˚C/W

θ

JC

(SO Package) 172˚C/W

θ

JA

(MSOP) 210˚C/W

θ

JA

(MSOP) 56˚C/W

θ

JC

Electrical Characteristics (Notes 1, 2)

TA= 25˚C

Parameter Conditions Min Typ Max Units

Operating Supply Voltage (V
LM386N-1, -3, LM386M-1, LM386MM-1 4 12 V
LM386N-4 518V
Quiescent Current (I
Output Power (P

)V

Q

)

OUT

LM386N-1, LM386M-1, LM386MM-1 V
LM386N-3 V
LM386N-4 V
Voltage Gain (A

)V

V

Bandwidth (BW) V
Total Harmonic Distortion (THD) V

Power Supply Rejection Ratio (PSRR) V

Input Resistance (R
Input Bias Current (I

Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 2: AbsoluteMaximum Ratings indicate limits beyond which damage to the device may occur.Operating Ratings indicate conditions for which the device is func-

tional, but donot guarantee specific performance limits. Electrical Characteristics state DC andAC electrical specifications under particular test conditions whichguar­antee 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 resis­tance 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.

) 50 kΩ

IN

BIAS

)

S

= 6V, VIN=0 4 8 mA

S

= 6V, RL=8Ω, THD = 10% 250 325 mW

S

= 9V, RL=8Ω, THD = 10% 500 700 mW

S

= 16V, RL=32Ω, THD = 10% 700 1000 mW

S

= 6V, f = 1 kHz 26 dB

S

10 µF from Pin 1 to 8 46 dB

= 6V, Pins 1 and 8 Open 300 kHz

S

= 6V, RL=8Ω,P

S

f = 1 kHz, Pins 1 and 8 Open

= 6V, f = 1 kHz, C

S

Pins 1 and 8 Open, Referred to Output

)V

= 6V, Pins 2 and 3 Open 250 nA

S

= 125 mW 0.2 %

OUT

BYPASS

=10µF 50 dB

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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 kΩ resistor sets the gain at 20 (26 dB). If a capacitor
is put from pin 1 to 8, bypassing the 1.35 kΩ 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 cou­pling 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 fre­quency response for individual applications. For example,
we can compensate poor speaker bass response by fre­quency shaping the feedback path. This is done with a series
RC from pin 1 to 5 (paralleling the internal 15 kΩ resistor).
For 6 dB effective bass boost: R . 15 kΩ, the lowest value
for good stable operation is R = 10 kΩ if pin 8 is open. If pins
1 and 8 are bypassed then R as low as 2 kΩ can be used.
This restriction is because the amplifier is only compensated
for closed-loop gains greater than 9.

LM386

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 kΩ 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 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 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 capacitively coupled.

When using the LM386 with higher gains (bypassing the

1.35 kΩ resistor between pins 1 and 8) it is necessary to by­pass 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

LM386

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

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Voltage Gain vs Frequency

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Device Dissipation vs Output
Power—4Ω Load

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Distortion vs Frequency

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Device Dissipation vs Output
Power—8Ω Load

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Distortion vs Output Power

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Device Dissipation vs Output
Power—16Ω Load

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DS006976-18

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Typical Applications

LM386

Amplifier with Gain = 20

Minimum Parts

Amplifier with Gain = 50

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Amplifier with Gain = 200

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Low Distortion Power Wienbridge Oscillator

Amplifier with Bass Boost

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Square Wave Oscillator

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DS006976-9

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Typical Applications (Continued)

LM386

Frequency Response with Bass Boost

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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

SO Package (M)

Order Number LM386M-1

NS Package Number M08A

LM386

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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

LM386

8-Lead (0.118” Wide) Molded Mini Small Outline Package

Order Number LM386MM-1

NS Package Number MUA08A

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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

LM386 Low Voltage Audio Power Amplifier

Dual-In-Line Package (N)

Order Number LM386N-1, LM386N-3 or LM386N-4

NS Package Number N08E

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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

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 effectiveness.

labeling, can be reasonably expected to result in a
significant injury to the user.

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