LF347M/NOPB - NATIONAL SEMICONDUCTOR

LF147,LF347

LF147/LF347 Wide Bandwidth Quad JFET Input Operational Amplifiers

Literature Number: SNOSBH1C

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

Ω

nLow total harmonic distortion: ≤0.02%

nLow 1/f noise corner: 50 Hz

nFast settling time to 0.01%: 2 µs

Simplified Schematic

⁄

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

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)

max 150˚C 150˚C

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

≤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

Input Offset Voltage R

=10 kΩ,T

=25˚C 1 5 3 5 5 10 mV

Over Temperature 8 7 13 mV

∆V

/∆T Average TC of Input Offset R

=10 kΩ10 10 10 µV/˚C

Voltage

Input Offset Current T

=25˚C, (Notes 7, 8) 25 100 25 100 25 100 pA

Over Temperature 25 4 4 nA

Input Bias Current T

=25˚C, (Notes 7, 8) 50 200 50 200 50 200 pA

Over Temperature 50 8 8 nA

Input Resistance T

=25˚C 10

Ω

VOL

Large Signal Voltage Gain V

=±15V, T

=25˚C 50 100 50 100 25 100 V/mV

=±10V, R

=2 kΩ

Over Temperature 25 25 15 V/mV

Output Voltage Swing V

=±15V, R

=10 kΩ±12 ±13.5 ±12 ±13.5 ±12 ±13.5 V

Input Common-Mode Voltage V

=±15V ±11 +15 ±11 +15 ±11 +15 V

Range −12 −12 −12 V

CMRR Common-Mode Rejection Ratio R

≤10 kΩ80 100 80 100 70 100 dB

PSRR Supply Voltage Rejection Ratio (Note 9) 80 100 80 100 70 100 dB

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

=25˚C, −120 −120 −120 dB

f=1 Hz−20 kHz

(Input Referred)

SR Slew Rate V

=±15V, T

=25˚C 8 13 8 13 8 13 V/µs

GBW Gain-Bandwidth Product V

=±15V, T

=25˚C 2.2 4 2.2 4 2.2 4 MHz

Equivalent Input Noise Voltage T

=25˚C, R

=100Ω,202020

f=1000 Hz

Equivalent Input Noise Current T

=25˚C, f=1000 Hz 0.01 0.01 0.01

THD Total Harmonic Distortion A

=+10, R

=10k,

=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

=2 kΩ,C

=10 pF

Small Signal Inverting

00564704

Small Signal Non-Inverting

00564705

Large Signal Inverting

00564706

Large Signal Non-Inverting

00564707

Current Limit (R

=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

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

≥V

•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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www.national.com

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.

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