Low Voltage Audio Power Amplifier
General Description
isapoweramplifierdesignedforuseinlowvolt-
ageconsumerapplications.Thegainisinternallysetto20to
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,makingthe
Features
nBattery operation
nMinimum external parts
nWidesupplyvoltagerange:4V–12V
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)
nAvailablein8pinSOPpackage
Applications
nAM-FMradioamplifiers
nPortabletapeplayeramplifiers
nIntercoms
nTVsoundsystems
nLinedrivers
nUltrasonicdrivers
nSmallservodrivers
nPowerconverters
Equivalent Schematic and Connection Diagrams
Small Outline,
Wing Shing Computer Components Co., (H.K.)Ltd. Tel:(852)2341 9276 Fax:(852)2797 8153
Homepage: http://www.wingshing.com E-mail: wsccltd@hkstar.com
Low Voltage
Audio Power Amplifier
WS386M-1 ideal for battery operation
Pin Connection
Dual in Line Package
and DIP package
Ordering Information
PART NO.
PACKAGE
SOP-8
8-1
LM386-1
The LM386-1
LM386M-1
LM386N-1
T
A
= 25˚C
Parameter Conditions Min Typ Max Units
Operating Supply Voltage (V
S
)
Quiescent Current (I
Q
)V
S
= 6V, V
IN
=0 4 8 mA
Output Power (P
OUT
)
S
= 6V, R
L
=8Ω, THD = 10% 250 325 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.
Note3:Foroperationinambienttemperaturesabove25˚C,thedevicemustbederatedbasedona150˚Cmaximumjunctiontemperatureand
athermalresistanceof170˚C/Wforthesmalloutlinepackage.
AbsoluteMaximumRatingsDual-In-LinePackage
Soldering (10 sec) +260˚C
Small Outline Package
(SOIC)
Vapor Phase (60 sec) +215˚C
Infrared (15 sec) +220˚C
Electrical Characteristics (Notes 1, 2)
4
12
V
V
,Vcc=6V,R =8 ,f=1KH , unless otherwise specified
Z
Pins 1 and 8 Open
15V
Soldering Information
Supply Voltage
(WS386-1)
Package Dissipation(Note3)
(WS386N) 1.25W
0.73W
(WS386M)
.4V
+
-
65 C to +150 C
0 C to+70 C
+150 C
Input Voltage
Storage Temperature
Junction Temperature
Operating Temperature
-
8-2
LM386-1
50
0
700
V s = 9V,RL =8 , THD =10%
Bandwidth (BW)
Vs = 6V,10uF from Pin 1 to 8
60
kHz
Application Hints
GAIN CONTROL amoreversatileamplifier,twopins(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.
withhighergains(bypassingthe
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.
8
7
6
1
90
5
90
2
4B
Y
3
4A
0X
1405
Gain
-input
+input
GND
GND
VOUT
VCC
100
BYPASS
Gain
390
1015
1405
1405
120
7
8
120
120
120
550
600
600
750
440
4A
4B
5
6
2
3
Coordinates
Pad N Pad Name XY
975
665
100
Chip size 1.4 x 1.6 mm
Pad Location
Pad Location Coordinates
1
8-3
LM386-1
To make LM386-1
When using LM386-1
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
Voltage Gain vs Frequency Distortion vs Frequency Distortion vs Output Power
Device Dissipation vs Output
Power—4ΩLoad Device Dissipation vs Output
Power—8ΩLoad Device Dissipation vs Output
Power—16ΩLoad
8-4
LM386-1
Typical Applications
Amplifier with Gain = 20
Minimum Parts Amplifier with Gain = 200
Amplifier with Gain = 50 Low Distortion Power Wienbridge Oscillator
Amplifier with Bass Boost Square Wave Oscillator
8-5
LM386-1
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
AM Radio Power Amplifier
8-6
LM386-1
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Dual-In-LinePackage
8-7
LM386N-1
Physical Dimensions inches (millimeters) unless otherwise noted
SO Package
8-8
LM386-1
LM386M-1