LF444
LF444 Quad Low Power JFET Input Operational Amplifier
Literature Number: SNOSC04C
LF444
Quad Low Power JFET Input Operational Amplifier
General Description
The LF444 quad low power operational amplifier provides
many of the same AC characteristics as the industry stan-
dard LM148 while greatly improving the DC characteristics
of the LM148. The amplifier has the same bandwidth, slew
rate, and gain (10 kΩload) as the LM148 and only draws
one fourth the supply current of the LM148. In addition the
well matched high voltage JFET input devices of the LF444
reduce the input bias and offset currents by a factor of
10,000 over the LM148. The LF444 also has a very low
equivalent input noise voltage for a low power amplifier.
The LF444 is pin compatible with the LM148 allowing an
immediate 4 times reduction in power drain in many appli-
cations. The LF444 should be used wherever low power
dissipation and good electrical characteristics are the major
considerations.
Features
n
1
⁄
4
supply current of a LM148: 200 µA/Amplifier (max)
nLow input bias current: 50 pA (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: 50k (min)
Simplified Schematic
1/4 Quad
00915601
Ordering Information
LF444XYZ
Xindicates electrical grade
Yindicates temperature range
“M” for military, “C” for commercial
Zindicates package type “D”, “M” or “N”
Connection Diagram
Dual-In-Line Package
00915602
Top View
Order Number LF444CM, LF444CMX,
LF444ACN, LF 444CN or LF444MD/883
See NS Package Number D14E, M14A or N14A
BI-FET™and BI-FET II™are trademarks of National Semiconductor Corporation.
August 2000
LF444 Quad Low Power JFET Input Operational Amplifier
© 2004 National Semiconductor Corporation DS009156 www.national.com
Absolute Maximum Ratings (Note 11)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
LF444A LF444
Supply Voltage ±22V ±18V
Differential Input Voltage ±38V ±30V
Input Voltage Range ±19V ±15V
(Note 1)
Output Short Circuit Continuous Continuous
Duration (Note 2)
D Package N, M Packages
Power Dissipation 900 mW 670 mW
(Notes 3, 9)
T
j
max 150˚C 115˚C
θ
jA
(Typical) 100˚C/W 85˚C/W
LF444A/LF444
Operating Temperature Range (Note 4)
Storage Temperature Range −65˚C ≤T
A
≤150˚C
ESD Tolerance (Note 10) Rating to
be determined
Soldering Information
Dual-In-Line Packages
(Soldering, 10 sec.) 260˚C
Small Outline Package
Vapor Phase (60 sec.) 215˚C
Infrared (15 sec.) 220˚C
See AN-450 “Surface Mounting Methods and Their Effect on
Product Reliability” for other methods of soldering surface
mount devices.
DC Electrical Characteristics (Note 5)
Symbol Parameter Conditions LF444A LF444 Units
Min Typ Max Min Typ Max
V
OS
Input Offset Voltage R
S
= 10k, T
A
= 25˚C 2 5 3 10 mV
0˚C ≤T
A
≤+70˚C 6.5 12 mV
−55˚C ≤T
A
≤+125˚C 8 mV
∆V
OS
/∆T Average TC of Input R
S
=10kΩ10 10 µV/˚C
Offset Voltage
I
OS
Input Offset Current V
S
=±15V T
j
= 25˚C 5 25 5 50 pA
(Notes 5, 6) 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 5, 6) 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 50 100 25 100 V/mV
Gain R
L
=10kΩ,T
A
= 25˚C
Over Temperature 25 15 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 7) 80 100 70 90 dB
Rejection Ratio
I
S
Supply Current 0.6 0.8 0.6 1.0 mA
LF444
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AC Electrical Characteristics (Note 5)
Symbol Parameter Conditions LF444A LF444 Units
Min Typ Max Min Typ Max
Amplifier-to-Amplifier −120 −120 dB
Coupling
SR Slew Rate V
S
=±15V, T
A
= 25˚C 1 1 V/µs
GBW Gain-Bandwidth Product V
S
=±15V, T
A
= 25˚C 1 1 MHz
e
n
Equivalent Input Noise Voltage T
A
= 25˚C, R
S
= 100Ω,35 35
f=1kHz
i
n
Equivalent Input Noise Current T
A
= 25˚C,f=1kHz 0.01 0.01
Note 1: Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage.
Note 2: 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 3: For operating at elevated temperature, these devices must be derated based on a thermal resistance of θjA.
Note 4: The LF444A is available in both the commercial temperature range 0˚C ≤TA≤70˚C and the military temperature range −55˚C ≤TA≤125˚C. The LF444
is available in the commercial temperature range only. The temperature range is designated by the position just before the package type in the device number. A
“C” indicates the commercial temperature range and an “M” indicates the military temperature range. The military temperature range is available in “D” package only.
Note 5: Unless otherwise specified the specifications apply over the full temperature range and for VS=±20V for the LF444A and for VS=±15V for the LF444.
VOS,I
B, and IOS are measured at VCM =0.
Note 6: 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 7: 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 LF444 and from ±20V to ±5V for the LF444A.
Note 8: Refer to RETS444X for LF444MD military specifications.
Note 9: Max. Power Dissipation is defined by the package characteristics. Operating the part near the Max. Power Dissipation may cause the part to operate outside
guaranteed limits.
Note 10: Human body model, 1.5 kΩin series with 100 pF.
Note 11: 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. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee 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.
Typical Performance Characteristics
Input Bias Current Input Bias Current
00915612
00915613
LF444
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Typical Performance Characteristics (Continued)
Supply Current
Positive Common-Mode
Input Voltage Limit
00915614 00915615
Negative Common-Mode
Input Voltage Limit Positive Current Limit
00915616
00915617
Negative Current Limit Output Voltage Swing
00915618 00915619
LF444
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Typical Performance Characteristics (Continued)
Output Voltage Swing Gain Bandwidth
00915620 00915621
Bode Plot Slew Rate
00915622 00915623
Distortion vs Frequency
Undistorted Output
Voltage Swing
00915624 00915625
LF444
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Typical Performance Characteristics (Continued)
Open Loop
Frequency Response
Common-Mode
Rejection Ratio
00915626 00915627
Power Supply
Rejection Ratio
Equivalent Input
Noise Voltage
00915628 00915629
Open Loop Voltage Gain Output Impedance
00915630 00915631
LF444
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Typical Performance Characteristics (Continued)
Inverter Settling Time
00915632
Pulse Response R
L
=10kΩ,C
L
=10pF
Small Signal Inverting
00915606
Small Signal Non-Inverting
00915607
Large Signal Inverting
00915608
Large Signal Non-Inverting
00915609
Application Hints
This device is a quad low power op amp with JFET input
devices ( BI-FET™). These JFETs have large reverse break-
down voltages from gate to source and drain eliminating the
need for clamps across the inputs. Therefore, large differen-
tial input voltages can easily be accommodated without a
large increase in input current. The maximum differential
input voltage is independent of the supply voltages. How-
ever, neither of the input voltages should be allowed to
exceed the negative supply as this will cause large currents
to flow which can result in a destroyed unit.
LF444
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Application Hints (Continued)
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. If the amplifier is forced to
drive heavier load currents, however, an increase in input
offset voltage may occur on the negative voltage swing and
finally reach an active current limit on both positive and
negative swings.
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 consequently 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.
LF444
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Typical Application
pH Probe Amplifier/Temperature Compensator
00915610
***For R2 = 50k, R4 = 330k ±1%
For R2 = 100k, R4 = 75k ±1%
For R2 = 200k, R4 = 56k ±1%
**Polystyrene
*Film resistor type RN60C
To calibrate, insert probe in pH =7 solution. Set the “TEMPERATURE ADJUST” pot, R2, to correspond to the solution temperature: full clockwise for 0˚C, and
proportionately for intermediate temperatures, using a turns-counting dial. Then set “CALIBRATE” pot so output reads 7V.
Typical probe = Ingold Electrodes #465-35
LF444
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Detailed Schematic
1/4 Quad
00915611
LF444
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Physical Dimensions inches (millimeters)
unless otherwise noted
Order Number LF444MD/883
See NS Package Number D14E
Order Number LF444CM or LF444CMX
See NS Package Number M14A
LF444
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LF444ACN or LF444CN
See NS Package Number N14A
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www.national.com
LF444 Quad Low Power JFET Input Operational Amplifier
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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