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National Semiconductor

LM386 Datasheet

Low Voltage Audio Power Amplifier

LM386 Datasheet Preview

January 2000
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.
n Battery operation
n Minimum external parts
n Wide supply voltage range: 4V–12V or 5V–18V
n Low quiescent current drain: 4 mA
n Voltage gains from 20 to 200
n Ground referenced input
n Self-centering output quiescent voltage
n Low distortion
n Available in 8 pin MSOP package
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
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
Page 1

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)
Input Voltage
Storage Temperature
Operating Temperature
Junction Temperature
Soldering Information
−65˚C to +150˚C
0˚C to +70˚C
Dual-In-Line Package
Soldering (10 sec)
Small Outline Package
Vapor Phase (60 sec)
Infrared (15 sec)
See AN-450 “Surface Mounting Methods and Their Effect
on Product Reliability” for other methods of soldering
surface mount devices.
Thermal Resistance
θJC (SO Package)
θJA (SO Package)
Electrical Characteristics (Notes 1, 2)
TA = 25˚C
Min Typ Max Units
Operating Supply Voltage (VS)
LM386N-1, -3, LM386M-1, LM386MM-1
4 12 V
5 18 V
Quiescent Current (IQ)
Output Power (POUT)
LM386N-1, LM386M-1, LM386MM-1
Voltage Gain (AV)
VS = 6V, VIN = 0
VS = 6V, RL = 8, THD = 10%
VS = 9V, RL = 8, THD = 10%
VS = 16V, RL = 32, THD = 10%
VS = 6V, f = 1 kHz
10 µF from Pin 1 to 8
250 325
500 700
700 1000
Bandwidth (BW)
Total Harmonic Distortion (THD)
VS = 6V, Pins 1 and 8 Open
VS = 6V, RL = 8, POUT = 125 mW
f = 1 kHz, Pins 1 and 8 Open
300 kHz
0.2 %
Power Supply Rejection Ratio (PSRR)
VS = 6V, f = 1 kHz, CBYPASS = 10 µF
Pins 1 and 8 Open, Referred to Output
50 dB
Input Resistance (RIN)
Input Bias Current (IBIAS)
VS = 6V, Pins 2 and 3 Open
50 k
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 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.
Page 2

Application Hints
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 kresistor sets the gain at 20 (26 dB). If a capacitor
is put from pin 1 to 8, bypassing the 1.35 kresistor, 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 kresistor).
For 6 dB effective bass boost: R 15 k, the lowest value
for good stable operation is R = 10 kif pin 8 is open. If pins
1 and 8 are bypassed then R as low as 2 kcan be used.
This restriction is because the amplifier is only compensated
for closed-loop gains greater than 9.
The schematic shows that both inputs are biased to ground
with a 50 kresistor. 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 kit 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 k, 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 kresistor 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.
Page 3
Part Number LM386
Manufactur National Semiconductor
Description Low Voltage Audio Power Amplifier
Total Page 9 Pages
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