LF442
LF442 Dual Low Power JFET Input Operational Amplifier
Literature Number: SNOSC03C
LF442
Dual Low Power JFET Input Operational Amplifier
General Description
The LF442 dual low power operational amplifiers provide
many of the same AC characteristics as the industry stan-
dard LM1458 while greatly improving the DC characteristics
of the LM1458. The amplifiers have the same bandwidth,
slew rate, and gain (10 kΩload) as the LM1458 and only
draw one tenth the supply current of the LM1458. In addition
the well matched high voltage JFET input devices of the
LF442 reduce the input bias and offset currents by a factor of
10,000 over the LM1458. A combination of careful layout
design and internal trimming guarantees very low input offset
voltage and voltage drift. The LF442 also has a very low
equivalent input noise voltage for a low power amplifier.
The LF442 is pin compatible with the LM1458 allowing an
immediate 10 times reduction in power drain in many appli-
cations. The LF442 should be used where low power dissi-
pation and good electrical characteristics are the major con-
siderations.
Features
n1/10 supply current of a LM1458: 400 µA (max)
nLow input bias current: 50 pA (max)
nLow input offset voltage: 1 mV (max)
nLow input offset voltage drift: 10 µV/˚C (max)
nHigh gain bandwidth: 1 MHz
nHigh slew rate: 1 V/µs
nLow noise voltage for low power:
nLow input noise current:
nHigh input impedance: 10
12
Ω
nHigh gain V
O
=±10V, R
L
= 10k: 50k (min)
Typical Connection
00915501
Ordering Information
LF442XYZ
Xindicates electrical grade
Yindicates temperature range
“M” for military
“C” for commercial
Zindicates package type
“H” or “N”
Connection Diagrams
Metal Can Package
00915502
Pin 4 connected to case
Top View
Order Number LF442AMH or LF442MH/883
See NS Package Number H08A
Dual-In-Line Package
00915504
Top View
Order Number LF442ACN or LF442CN
See NS Package Number N08E
BI-FET II™is a trademark of National Semiconductor Corporation.
August 2000
LF442 Dual Low Power JFET Input Operational Amplifier
© 2004 National Semiconductor Corporation DS009155 www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
LF442A LF442
Supply Voltage ±22V ±18V
Differential Input Voltage ±38V ±30V
Input Voltage Range ±19V ±15V
(Note 2)
Output Short Circuit Continuous Continuous
Duration (Note 3)
H Package N Package
T
j
max 150˚C 115˚C
H Package N Package
θ
JA
(Typical)
(Note 4)
(Note 5)
65˚C/W
165˚C/W
114˚C/W
152˚C/W
θ
JC
(Typical) 21˚C/W
Operating Temperature (Note 5) (Note 5)
Range
Storage −65˚C≤T
A
≤150˚C−65˚C≤T
A
≤150˚C
Temperature Range
Lead Temperature 260˚C 260˚C
(Soldering, 10 sec.)
ESD Tolerance Rating to be determined
DC Electrical Characteristics (Note 7)
Symbol Parameter Conditions LF442A LF442 Units
Min Typ Max Min Typ Max
V
OS
Input Offset Voltage R
S
=10kΩ,T
A
= 25˚C 0.5 1.0 1.0 5.0 mV
Over Temperature 7.5 mV
∆V
OS
/∆T Average TC of Input R
S
=10kΩ7 10 7 µV/˚C
Offset Voltage
I
OS
Input Offset Current V
S
=±15V T
j
= 25˚C 5 25 5 50 pA
(Notes 7, 8) T
j
= 70˚C 1.5 1.5 nA
T
j
= 125˚C 10 nA
I
B
Input Bias Current V
S
=±15V T
j
= 25˚C 10 50 10 100 pA
(Notes 7, 8) T
j
= 70˚C 3 3 nA
T
j
= 125˚C 20 nA
R
IN
Input Resistance T
j
= 25˚C 10
12
10
12
Ω
A
VOL
Large Signal Voltage V
S
=±15V, V
O
=±10V, 50 200 25 200 V/mV
Gain R
L
=10kΩ,T
A
= 25˚C
Over Temperature 25 200 15 200 V/mV
V
O
Output Voltage Swing V
S
=±15V, R
L
=10kΩ±12 ±13 ±12 ±13 V
V
CM
Input Common-Mode ±16 +18 ±11 +14 V
Voltage Range −17 −12 V
CMRR Common-Mode R
S
≤10 kΩ80 100 70 95 dB
Rejection Ratio
PSRR Supply Voltage (Note 9) 80 100 70 90 dB
Rejection Ratio
I
S
Supply Current 300 400 400 500 µA
LF442
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AC Electrical Characteristics (Note 7)
Symbol Parameter Conditions LF442A LF442 Units
Min Typ Max Min Typ Max
Amplifier to Amplifier T
A
= 25˚C,f=1Hz-20 kHz −120 −120 dB
Coupling (Input Referred)
SR Slew Rate V
S
=±15V, T
A
= 25˚C 0.8 1 0.6 1 V/µs
GBW Gain-Bandwidth Product V
S
=±15V, T
A
= 25˚C 0.8 1 0.6 1 MHz
e
n
Equivalent Input Noise T
A
= 25˚C, R
S
= 100Ω,35 35
Voltage f=1kHz
i
n
Equivalent Input Noise T
A
= 25˚C,f=1kHz 0.01 0.01
Current
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits.
Note 2: Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage.
Note 3: Any of the amplifier outputs can be shorted to ground indefinitely, however, more than one should not be simultaneously shorted as the maximum junction
temperature will be exceeded.
Note 4: The value given is in 400 linear feet/min air flow.
Note 5: The value given is in static air.
Note 6: These devices are available in both the commercial temperature range 0˚C ≤TA≤70˚C and the military temperature range −55˚C ≤TA≤125˚C. The
temperature range is designated by the position just before the package type in the device number. A “C” indicates the commercial temperature range andan“M”
indicates the military temperature range. The military temperature range is available in “H” package only.
Note 7: Unless otherwise specified, the specifications apply over the full temperature range and for VS=±20V for the LF442A and for VS=±15V for the LF442.
VOS,I
B, and IOS are measured at VCM =0.
Note 8: The input bias currents are junction leakage currents which approximately double for every 10˚C increase in the junction temperature, Tj. Due to limited
production test time, the input bias currents measured are correlated to junction temperature. In normal operation the junction temperature rises above the ambient
temperature as a result of internal power dissipation, PD.T
j=T
A+θjAPDwhere θjA is the thermal resistance from junction to ambient. Use of a heat sink is
recommended if input bias current is to be kept to a minimum.
Note 9: Supply voltage rejection ratio is measured for both supply magnitudes increasing or decreasing simultaneously in accordance with common practice from
±15V to ±5V for the LF442 and ±20V to ±5V for the LF442A.
Note 10: Refer to RETS442X for LF442MH military specifications.
Simplified Schematic
1/2 Dual
00915503
LF442
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Typical Performance Characteristics
Input Bias Current Input Bias Current
00915517 00915518
Supply Current
Positive Common-Mode
Input Voltage Limit
00915519 00915520
Negative Common-Mode
Input Voltage Limit Positive Current Limit
00915521 00915522
LF442
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Typical Performance Characteristics (Continued)
Negative Current Limit Output Voltage Swing
00915523 00915524
Output Voltage Swing Gain Bandwidth
00915525 00915526
Bode Plot Slew Rate
00915527 00915528
LF442
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Typical Performance Characteristics (Continued)
Distortion vs Frequency
Undistorted Output Voltage
Swing
00915529 00915530
Open Loop Frequency
Response
Common-Mode Rejection
Ratio
00915531 00915532
Power Supply Rejection
Ratio
Equivalent Input Noise
Voltage
00915533 00915534
LF442
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Typical Performance Characteristics (Continued)
Open Loop Voltage Gain Output Impedance
00915535 00915536
Inverter Settling Time
00915537
LF442
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Pulse Response R
L
=10kΩ,C
L
=10pF
Small Signal Inverting
00915507
Small Signal Non-Inverting
00915508
Large Signal Inverting
00915509
Large Signal Non-Inverting
00915510
LF442
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Application Hints
This device is a dual low power op amp with internally
trimmed input offset voltages and JFET input devices (BI-
FET II). These JFETs have large reverse breakdown volt-
ages from gate to source and drain eliminating the need for
clamps across the inputs. Therefore, large differential input
voltages can easily be accommodated without a large in-
crease in input current. The maximum differential input volt-
age is independent of the supply voltages. However, neither
of the input voltages should be allowed to exceed the nega-
tive supply as this will cause large currents to flow which can
result in a destroyed unit.
Exceeding the negative common-mode limit on either input
will force the output to a high state, potentially causing a
reversal of phase to the output. Exceeding the negative
common-mode limit on both inputs will force the amplifier
output to a high state. In neither case does a latch occur
since raising the input back within the common-mode range
again puts the input stage and thus the amplifier in a normal
operating mode.
Exceeding the positive common-mode limit on a single input
will not change the phase of the output; however, if both
inputs exceed the limit, the output of the amplifier will be
forced to a high state.
The amplifiers will operate with a common-mode input volt-
age equal to the positive supply; however, the gain band-
width and slew rate may be decreased in this condition.
When the negative common-mode voltage swings to within
3V of the negative supply, an increase in input offset voltage
may occur.
Each amplifier is individually biased to allow normal circuit
operation with power supplies of ±3.0V. Supply voltages less
than these may degrade the common-mode rejection and
restrict the output voltage swing.
The amplifiers will drive a 10 kΩload resistance to ±10V
over the full temperature range.
Precautions should be taken to ensure that the power supply
for the integrated circuit never becomes reversed in polarity
or that the unit is not inadvertently installed backwards in a
socket as an unlimited current surge through the resulting
forward diode within the IC could cause fusing of the internal
conductors and result in a destroyed unit.
As with most amplifiers, care should be taken with lead
dress, component placement and supply decoupling in order
to ensure stability. For example, resistors from the output to
an input should be placed with the body close to the input to
minimize “pick-up” and maximize the frequency of the feed-
back pole by minimizing the capacitance from the input to
ground.
A feedback pole is created when the feedback around any
amplifier is resistive. The parallel resistance and capacitance
from the input of the device (usually the inverting input) to AC
ground set the frequency of the pole. In many instances the
frequency of this pole is much greater than the expected 3
dB frequency of the closed loop gain and consequenty there
is negligible effect on stability margin. However, if the feed-
back pole is less than approximately 6 times the expected 3
dB frequency a lead capacitor should be placed from the
output to the input of the op amp. The value of the added
capacitor should be such that the RC time constant of this
capacitor and the resistance it parallels is greater than or
equal to the original feedback pole time constant.
Typical Applications
Battery Powered Strip Chart Preamplifier
00915511
Runs from 9v batteries (±9V supplies)
Fully settable gain and time constant
Battery powered supply allows direct plug-in interface to strip chart recorder without common-mode problems
LF442
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Typical Applications (Continued)
“No FET” Low Power V→F Converter
00915512
Trim 1M pot for 1 kHz full-scale output
15 mW power drain
No integrator reset FET required
Mount D1 and D2 in close proximity
1% linearity to 1 kHz
High Efficiency Crystal Oven Controller
00915513
•T
control
= 75˚C
•A1’s output represents the amplified difference between the LM335 temperature sensor and the crystal oven’s temperature
•A2, a free running duty cycle modulator, drives the LM395 to complete a servo loop
•Switched mode operation yields high efficiency
•1% metal film resistor
LF442
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Typical Applications (Continued)
Conventional Log Amplifier
00915514
RT= Tel Labs type Q81
Trim 5k for 10 µA through the 5k–120k combination
*1% film resistor
Unconventional Log Amplifier
00915515
Q1, Q2, Q3 are included on LM389 amplifier chip which is temperature-stabilized by the LM389 and Q2-Q3, which act as a heater-sensor pair.
Q1, the logging transistor, is thus immune to ambient temperature variation and requires no temperature compensation at all.
LF442
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Detailed Schematic
1/2 Dual
00915516
LF442
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Physical Dimensions inches (millimeters)
unless otherwise noted
TO-5 Metal Can Package (H)
Order Number LF442AMH or LF442MH/883
NS Package Number H08A
LF442
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Molded Dual-In-Line Package (N)
Order Number LF442ACN or LF442CN
NS Package Number N08E
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www.national.com
LF442 Dual Low Power JFET Input Operational Amplifier
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