PJ386
Low Voltage Audio Power Amplifier
1-6
2003/10.ver.A
he PJ386 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 up to 200.
The inputs are ground referenced while the output is
automatically biased to one half the supply voltage.The
quiescent power drain is only 24 milliwatts when operating
from a 6 volt supply,making the PJ386 ideal for battery
operation.
Battery operation
Minimum external parts
Wide supply voltage range 4-12 Volt
Low quiescent current drain 4mA
Voltage gains from 20 to 200
Ground referenced input
self-centering output quiescent voltage
Low distortion
Eight pin dual-in-line package
AM-FM radio amplifiers
Portable tape player amplifiers
Intercoms
TV sound systems
Line drivers
Ultrasonic drivers
Small servo drivers
Power converters
T
Device
Operating Temperature
Package
PJ386CD DIP-8
PJ386CS
-20
o
C TO +85
o
C
SOP-8
FEATURES
APPLICATIONS
EQUIVALENT CIRCUIT
ORDERING INFORMATION
DIP-8
SOP-8
P
in : 1. Gain 5. Output
2. -Input 6. V+
3. +Input 7. Bypass
4. Gnd 8. Gain
PJ386
Low Voltage Audio Power Amplifier
2-6
2003/10.ver.A
Characteristic
Symbol
Value Unit
Supply Voltage
V+
15
V
Power Dissipation DIP-8
SOP-8
P
D
700
300
mW
Input Voltage Range
V
in
0.4
V
Operating Temperature Range
T
opr
-20 ~ +85
o
C
Storage Temperature Range
T
stg
-40 ~ +125
o
C
Parameter
Conditions
Min.
Typ.
Max.
Units
Quiescent Circuit Current(I
Q
)
V
IN
=0
4
8
mA
Output Power (P
OUT
)
V
s
=6V , R
L
=8,THD=10%
V
s
= 9V , R
L
=8,THD=10%
250
500
325
700
mW
mW
Voltage Gain (Av)
D-Type
V
s
=6V,f=1KHz
10F from Pin 1 to 8
26
46
dB
dB
Bandwidth (BW) D-Type
V
S
=6V, Pins 1 and 8 Open
10F from Pin 1 to 8
300
60
KHz
Total Harmonic Distortion(THD)
(D-Type)
V
S
=6V, R
L
=8,P
OUT
=125mW
f=1KHz, Pins 1 and 8 open
0.2 %
Power Supply Rejection Ratio
(PSRR)
V
S
=6V,f=1KHz, C
BY PASS
=10F
Pins 1 and 8 Open, Referred to Output
50 dB
Input Resistance (R
IN
)
Input Bias Current (I
BIAS
)
V
S
=6V,Pins 2 and 3 Open
50
250
K
nA
(note 1) Set the maximum junction temperature to 125 and reduce the thermal resistance to 143/W when the ambient
temperature is high.
(note 2) Insert a 10resistor and 0.05F capacitor in series to ground terminal from pin 5.
ELECTRICAL CHARACTERISTICS
(T
A=
25)
TYPICAL APPLICATION
ABSOLUTE MAXIMUM RATINGS
(T
A=
25)
PJ386
PJ386
PJ386
Low Voltage Audio Power Amplifier
3-6
2003/10.ver.A
Amplifier with Bass Boost
Amplifier 2
Low Distortion Power Wienbrige Oscillator
Square Wave Oscillator
GAIN CONTROL
To make the PJ386 a more versatile amplifier, two pins ( 1 and 8 ) are provided for gain control. With pins 1 to 8 open the
1.35K
resistor sets the gain at 20 (26dB). If a capacitor is put from pin 1 to 8,bypassing the 1.35 K 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 frequen-cy
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 K
resistor). For 6 dB effective bass
boost: R
15 K ,the lowest values for good stable operation is Rmin=10 K if pin 8 is open.If pins 1 and 8 are bypassed
then R as low 2 K
can be used. This restriciton 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 with a 50 K resistor. The base current of the input transistors is
about 250nA , so the inputs are at about 12.5mV when left open. If the dc source resistance driving the PJ386 is higher than 250
K
it will contribute very little additional offset (about 2.5mV at the input, 50mV 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 2.5mV at the input , 50mV 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 PJ386 will higher gains (bypassing the 1.35 K
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 0.1F capacitor or a short to ground
depending on the dc source resistance on the driven input.
APPLICATION HINTS
TYPICAL CHARACTERISTICS
(
Ta=25)
PJ386
Low Voltage Audio Power Amplifier
4-6
2003/10.ver.A
Quiescent Current vs. Supply Voltage
Voltage Gain vs. Frequency
Total Harmonic Distortion vs. Frequency
(V
+
=6V, R
L
=8, Po=125mW,Av=26dB)
Maximum Output Voltage Swing vs. Supply Voltage
Power Supply Rejection Ratio vs. Frequency
(V
+
=6V,Av=26dB)
Total Harmonic Distortion vs. Output Power
(V
+
=6V, R
L
=8, f=1KHz)
PJ386
Low Voltage Audio Power Amplifier
5-6
2003/10.ver.A
Power Dissipation vs. Output Power(R
L
=4)
Power Dissipation vs. Output Power(R
L
=16)
Power Dissipation vs. AmbientTemperature
Power Dissipation vs. Output Power(R
L
=8)
Frequency Response with Base Boost
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