TL H 7841
LM381LM381A
Low
Noise
Dual
Preamplifier
July 1987
LM381 LM381A Low Noise Dual Preamplifier
General Description
The LM381 LM381A is a dual preamplifier for the amplifica-
tion of low level signals in applications requiring optimum
noise performance Each of the two amplifiers is completely
independent with individual internal power supply decou-
pler-regulator providing 120 dB supply rejection and 60 dB
channel separation Other outstanding features include high
gain (112 dB) large output voltage swing (V
CC
b
2V) p-p
and wide power bandwidth (75 kHz 20 Vp-p) The LM381
LM381A operates from a single supply across the wide
range of 9V to 40V
Either differential input or single ended input configurations
may be selected The amplifier is internally compensated
with the provision for additional external compensation for
narrow band applications For additional information see
AN-64 AN-104
Features
Y
Low noise
0 5 mV total input noise
Y
High gain
112 dB open loop
Y
Single supply operation
Y
Wide supply range 9V 40V
Y
Power supply rejection
120 dB
Y
Large output voltage swing (V
CC
b
2V)p-p
Y
Wide bandwidth 15 MHz unity gain
Y
Power bandwidth 75 kHz 20 Vp-p
Y
Internally compensated
Y
Short circuit protected
Schematic Diagram
TL H 7841 1
C1995 National Semiconductor Corporation
RRD-B30M115 Printed in U S A
Absolute Maximum Ratings
If Military Aerospace specified devices are required
please contact the National Semiconductor Sales
Office Distributors for availability and specifications
Supply Voltage
a
40V
Power Dissipation (Note 1)
1 56 W
Operating Temperature Range
0 C to
a
70 C
Storage Temperature Range
b
65 C to
a
150 C
Lead Temperature (Soldering 10 sec )
260 C
Electrical Characteristics
T
A
e
25 C V
CC
e
14V unless otherwise stated
Parameter
Conditions
Min
Typ
Max
Units
Voltage Gain
Open Loop (Differential Input) f
e
100 Hz
160 000
V V
Open Loop (Single Ended) f
e
100 Hz
320 000
V V
Supply Current
V
CC
9V to 40V R
L
e
%
10
mA
Input Resistance
(Positive Input)
100
kX
(Negative Input)
200
kX
Input Current
(Negative Input)
0 5
m
A
Output Resistance
Open Loop
150
X
Output Current
Source
8
mA
Sink
2
mA
Output Voltage Swing
Peak-to-Peak
V
CC
b
2
V
Unity Gain Bandwidth
15
MHz
Power Bandwidth
20 V
PP
(V
CC
e
24V)
75
kHz
Maximum Input Voltage
Linear Operation
300
mVrms
Supply Rejection Ratio
f
e
1 kHz
120
dB
Channel Separation
f
e
1 kHz
60
dB
Total Harmonic Distortion
60 dB Gain f
e
1 kHz
0 1
%
Total Equivalent Input
R
S
e
60X 10 10 000 Hz (Single Ended
Noise
Input Flat Gain Circuit A
V
e
1000)
LM381A
0 5
0 7
m
Vrms
LM381
0 5
1 0
m
Vrms
Note 1
For operation in ambient temperatures above 25 C the device must be derated based on a 150 C maximum junction temperature and a thermal resistance
of 80 C W junction to ambient
Connection Diagram
Dual-In-Line Package
TL H 7841 2
Top View
Order Number LM381N or LM381AN
See NS Package Number N14A
2
Typical Applications
Typical Tape Playback Amplifier
TL H 7841 3
Two-Pole Fast Turn-On NAB Tape Preamp
TL H 7841 5
Typical Magnetic Phono Preamp
TL H 7841 4
Audio Mixer
TL H 7841 6
Ultra-Low Distortion Amplifier
(A
V
e
10 THD
k
0 05% V
OUT
e
3 V
RMS
)
TL H 7841 7
3
Typical Performance Characteristics
Response
Large Signal Frequency
V
CC
vs I
CC
V
CC
Swing vs
P-P Output Voltage
% Distortion
Channel Separation
PSRR vs Frequency
Gain and Phase Response
Noise Voltage vs Frequency
Noise Current vs Frequency
Pulse Response
TL H 7841 8
4
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