LM386N - National Semiconductor - Datasheet.Directory

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 up to 200.

The inputs are ground referenced while the output is auto-

matically biased to one half the supply voltage. The quies-

cent 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: 4 mA

nVoltage gains from 20 to 200

nGround referenced input

nSelf-centering output quiescent voltage

nLow distortion

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

January 2000

LM386 Low Voltage Audio Power Amplifier

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

(DIP) 37˚C/W

(DIP) 107˚C/W

(SO Package) 35˚C/W

(SO Package) 172˚C/W

(MSOP) 210˚C/W

(MSOP) 56˚C/W

Electrical Characteristics (Notes 1, 2)

=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

6V, V

=048mA

Output Power (P

OUT

)

LM386N-1, LM386M-1, LM386MM-1 V

=6V, R

=8Ω, THD =10%250 325 mW

LM386N-3 V

=9V, R

=8Ω, THD =10%500 700 mW

LM386N-4 V

=16V, R

=32Ω, THD =10%700 1000 mW

Voltage Gain (A

6V, f =1 kHz 26 dB

10 µF from Pin 1 to 8 46 dB

Bandwidth (BW) V

=6V, Pins 1 and 8 Open 300 kHz

Total Harmonic Distortion (THD) V

=6V, R

=8Ω,P

OUT

=125 mW 0.2 %

f=1 kHz, Pins 1 and 8 Open

Power Supply Rejection Ratio (PSRR) V

=6V, f =1 kHz, C

BYPASS

=10 µF 50 dB

Pins 1 and 8 Open, Referred to Output

Input Resistance (R

) 50 kΩ

Input Bias Current (I

BIAS

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

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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 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

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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

LM386

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

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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

safety or effectiveness.

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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.