LF147/LF347
Wide Bandwidth Quad JFET Input Operational Amplifiers
General Description
The LF147 is a low cost, high speed quad JFET input
operational amplifier with an internally trimmed input offset
voltage (BI-FET II™technology). The device requires a low
supply current and yet maintains a large gain bandwidth
product and a fast slew rate. In addition, well matched high
voltage JFET input devices provide very low input bias and
offset currents. The LF147 is pin compatible with the stan-
dard LM148. This feature allows designers to immediately
upgrade the overall performance of existing LF148 and
LM124 designs.
The LF147 may be used in applications such as high speed
integrators, fast D/A converters, sample-and-hold circuits
and many other circuits requiring low input offset voltage,
low input bias current, high input impedance, high slew rate
and wide bandwidth. The device has low noise and offset
voltage drift.
Features
nInternally trimmed offset voltage: 5 mV max
nLow input bias current: 50 pA
nLow input noise current: 0.01 pA/√Hz
nWide gain bandwidth: 4 MHz
nHigh slew rate: 13 V/µs
nLow supply current: 7.2 mA
nHigh input impedance: 10
12
Ω
nLow total harmonic distortion: ≤0.02%
nLow 1/f noise corner: 50 Hz
nFast settling time to 0.01%: 2 µs
Simplified Schematic
1
⁄
4
Quad
00564713
Connection Diagram
Dual-In-Line Package
00564701
Note 1: LF147 available as per JM38510/11906.
Top View
Order Number LF147J, LF147J-SMD, LF347M,
LF347BN, LF347N, LF147J/883,
or JL147 BCA (Note 1)
See NS Package Number J14A, M14A or N14A
BI-FET II™is a trademark of National Semiconductor Corporation.
August 2000
LF147/LF347 Wide Bandwidth Quad JFET Input Operational Amplifiers
© 2004 National Semiconductor Corporation DS005647 www.national.com
Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
LF147 LF347B/LF347
Supply Voltage ±22V ±18V
Differential Input Voltage ±38V ±30V
Input Voltage Range ±19V ±15V
(Note 3)
Output Short Circuit Continuous Continuous
Duration (Note 4)
Power Dissipation 900 mW 1000 mW
(Notes 5, 11)
T
j
max 150˚C 150˚C
θ
jA
Ceramic DIP (J) Package 70˚C/W
Plastic DIP (N) Package 75˚C/W
Surface Mount Narrow (M) 100˚C/W
Surface Mount Wide (WM) 85˚C/W
LF147 LF347B/LF347
Operating Temperature (Note 6) (Note 6)
Range
Storage Temperature
Range −65˚C≤T
A
≤150˚C
Lead Temperature
(Soldering, 10 sec.) 260˚C 260˚C
Soldering Information
Dual-In-Line Package
Soldering (10 seconds) 260˚C
Small Outline Package
Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C
See AN-450 “Surface Mounting Methods and Their Effect
on Product Reliability” for other methods of soldering
surface mount devices.
ESD Tolerance (Note 12) 900V
DC Electrical Characteristics (Note 7)
Symbol Parameter Conditions LF147 LF347B LF347 Units
Min Typ Max Min Typ Max Min Typ Max
V
OS
Input Offset Voltage R
S
=10 kΩ,T
A
=25˚C 1 5 3 5 5 10 mV
Over Temperature 8 7 13 mV
∆V
OS
/∆T Average TC of Input Offset R
S
=10 kΩ10 10 10 µV/˚C
Voltage
I
OS
Input Offset Current T
j
=25˚C, (Notes 7, 8) 25 100 25 100 25 100 pA
Over Temperature 25 4 4 nA
I
B
Input Bias Current T
j
=25˚C, (Notes 7, 8) 50 200 50 200 50 200 pA
Over Temperature 50 8 8 nA
R
IN
Input Resistance T
j
=25˚C 10
12
10
12
10
12
Ω
A
VOL
Large Signal Voltage Gain V
S
=±15V, T
A
=25˚C 50 100 50 100 25 100 V/mV
V
O
=±10V, R
L
=2 kΩ
Over Temperature 25 25 15 V/mV
V
O
Output Voltage Swing V
S
=±15V, R
L
=10 kΩ±12 ±13.5 ±12 ±13.5 ±12 ±13.5 V
V
CM
Input Common-Mode Voltage V
S
=±15V ±11 +15 ±11 +15 ±11 +15 V
Range −12 −12 −12 V
CMRR Common-Mode Rejection Ratio R
S
≤10 kΩ80 100 80 100 70 100 dB
PSRR Supply Voltage Rejection Ratio (Note 9) 80 100 80 100 70 100 dB
I
S
Supply Current 7.2 11 7.2 11 7.2 11 mA
LF147/LF347
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AC Electrical Characteristics (Note 7)
Symbol Parameter Conditions LF147 LF347B LF347 Units
Min Typ Max Min Typ Max Min Typ Max
Amplifier to Amplifier Coupling T
A
=25˚C, −120 −120 −120 dB
f=1 Hz−20 kHz
(Input Referred)
SR Slew Rate V
S
=±15V, T
A
=25˚C 8 13 8 13 8 13 V/µs
GBW Gain-Bandwidth Product V
S
=±15V, T
A
=25˚C 2.2 4 2.2 4 2.2 4 MHz
e
n
Equivalent Input Noise Voltage T
A
=25˚C, R
S
=100Ω,202020
f=1000 Hz
i
n
Equivalent Input Noise Current T
j
=25˚C, f=1000 Hz 0.01 0.01 0.01
THD Total Harmonic Distortion A
V
=+10, R
L
=10k,
V
O
=20 Vp-p,
BW=20 Hz−20 kHz
<0.02 <0.02 <0.02 %
Note 2: 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 3: Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage.
Note 4: 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 5: For operating at elevated temperature, these devices must be derated based on a thermal resistance of θjA.
Note 6: The LF147 is available in the military temperature range −55˚C≤TA≤125˚C, while the LF347B and the LF347 are available in the commercial temperature
range 0˚C≤TA≤70˚C. Junction temperature can rise to Tjmax = 150˚C.
Note 7: Unless otherwise specified the specifications apply over the full temperature range and for VS=±20V for the LF147 and for VS=±15V for the LF347B/LF347.
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=TA+θjA PDwhere 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
VS=±5V to ±15V for the LF347 and LF347B and from VS=±20V to ±5V for the LF147.
Note 10: Refer to RETS147X for LF147D and LF147J military specifications.
Note 11: 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 12: Human body model, 1.5 kΩin series with 100 pF.
LF147/LF347
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Typical Performance Characteristics
Input Bias Current Input Bias Current
00564714 00564715
Supply Current
Positive Common-Mode
Input Voltage Limit
00564716
00564717
Negative Common-Mode
Input Voltage Limit Positive Current Limit
00564718
00564719
LF147/LF347
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Typical Performance Characteristics (Continued)
Negative Current Limit Output Voltage Swing
00564720 00564721
Output Voltage Swing Gain Bandwidth
00564722 00564723
Bode Plot Slew Rate
00564724 00564725
LF147/LF347
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Typical Performance Characteristics (Continued)
Distortion vs Frequency
Undistorted Output Voltage
Swing
00564726 00564727
Open Loop Frequency
Response
Common-Mode Rejection
Ratio
00564728 00564729
Power Supply Rejection
Ratio
Equivalent Input Noise
Voltage
00564730 00564731
LF147/LF347
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Typical Performance Characteristics (Continued)
Open Loop Voltage Gain Output Impedance
00564732 00564733
Inverter Settling Time
00564734
LF147/LF347
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Pulse Response R
L
=2 kΩ,C
L
=10 pF
Small Signal Inverting
00564704
Small Signal Non-Inverting
00564705
Large Signal Inverting
00564706
Large Signal Non-Inverting
00564707
Current Limit (R
L
=100Ω)
00564708
Application Hints
The LF147 is an op amp with an internally trimmed input
offset voltage and JFET input devices (BI-FET II). These
JFETs have large reverse breakdown voltages 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 increase in input current.
The maximum differential input voltage is independent of the
supply voltages. However, 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.
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.
LF147/LF347
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Application Hints (Continued)
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 by a zener reference
which allows normal circuit operation on ±4.5V power sup-
plies. Supply voltages less than these may result in lower
gain bandwidth and slew rate.
The LF147 will drivea2kΩload 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.
Detailed Schematic
00564709
LF147/LF347
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Typical Applications
Digitally Selectable Precision Attenuator
00564710
All resistors 1% tolerance
•Accuracy of better than 0.4% with standard 1% value resistors
No offset adjustment necessary
•Expandable to any number of stages
•Very high input impedance
A1 A2 A3 V
O
Attenuation
000 0
001 −1dB
010 −2dB
011 −3dB
100 −4dB
101 −5dB
110 −6dB
111 −7dB
LF147/LF347
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Typical Applications (Continued)
Long Time Integrator with Reset, Hold and Starting Threshold Adjustment
00564711
•V
OUT
starts from zero and is equal to the integral of the input voltage with respect to the threshold voltage:
•Output starts when V
IN
≥V
TH
•Switch S1 permits stopping and holding any output value
•Switch S2 resets system to zero
LF147/LF347
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Typical Applications (Continued)
Universal State Variable Filter
00564712
For circuit shown:
fo=3 kHz, fNOTCH=9.5 kHz
Q=3.4
Passband gain:
Highpass — 0.1
Bandpass — 1
Lowpass — 1
Notch — 10
•foxQ≤200 kHz
•10V peak sinusoidal output swing without slew limiting to 200 kHz
•See LM148 data sheet for design equations
LF147/LF347
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Physical Dimensions inches (millimeters) unless otherwise noted
Ceramic Dual-In-Line Package (J)
Order Number LF147J, LM147J-SMD or LF147J/883
NS Package Number J14A
S.O. Package (M)
Order Number LF347M or LF347MX
NS Package Number M14A
LF147/LF347
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Molded Dual-In-Line Package (N)
Order Number LF347BN or LF347N
NS Package Number N14A
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COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
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whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
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LF147/LF347 Wide Bandwidth Quad JFET Input Operational Amplifiers
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.
