LF398M National Semiconductor, LF398M Datasheet

AMP, MONO, SAMPLE & HOLD, 14SOIC

LF398M

Manufacturer Part Number
LF398M
Description
AMP, MONO, SAMPLE & HOLD, 14SOIC
Manufacturer
National Semiconductor
Datasheet

Specifications of LF398M

No. Of Amplifiers
1
Bandwidth
1MHz
Acquisition Time
20µs
Input Offset Voltage
2mV
Supply Voltage Range
± 5V To ± 18V
Amplifier Case Style
SOIC
No. Of Pins
14
Operating Temperature Range
0°C To
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

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© 2000 National Semiconductor Corporation
LF198/LF298/LF398, LF198A/LF398A
Monolithic Sample-and-Hold Circuits
General Description
The LF198/LF298/LF398 are monolithic sample-and-hold
circuits which utilize BI-FET technology to obtain ultra-high
dc accuracy with fast acquisition of signal and low droop
rate. Operating as a unity gain follower, dc gain accuracy is
0.002% typical and acquisition time is as low as 6 µs to
0.01%. A bipolar input stage is used to achieve low offset
voltage and wide bandwidth. Input offset adjust is accom-
plished with a single pin, and does not degrade input offset
drift. The wide bandwidth allows the LF198 to be included in-
side the feedback loop of 1 MHz op amps without having sta-
bility problems. Input impedance of 10
source impedances to be used without degrading accuracy.
P-channel junction FET’s are combined with bipolar devices
in the output amplifier to give droop rates as low as 5 mV/min
with a 1 µF hold capacitor. The JFET’s have much lower
noise than MOS devices used in previous designs and do
not exhibit high temperature instabilities. The overall design
guarantees no feed-through from input to output in the hold
mode, even for input signals equal to the supply voltages.
Typical Connection and Performance Curve
Functional Diagram
DS005692
10
DS005692-32
allows high
Features
n Operates from
n Less than 10 µs acquisition time
n TTL, PMOS, CMOS compatible logic input
n 0.5 mV typical hold step at C
n Low input offset
n 0.002% gain accuracy
n Low output noise in hold mode
n Input characteristics do not change during hold mode
n High supply rejection ratio in sample or hold
n Wide bandwidth
n Space qualified, JM38510
Logic inputs on the LF198 are fully differential with low input
current, allowing direct connection to TTL, PMOS, and
CMOS. Differential threshold is 1.4V. The LF198 will operate
from
An “A” version is available with tightened electrical
specifications.
±
5V to
±
18V supplies.
±
5V to
Acquisition Time
DS005692-1
±
18V supplies
h
= 0.01 µF
DS005692-16
www.national.com
July 2000

Related parts for LF398M

LF398M Summary of contents

Page 1

... Typical Connection and Performance Curve Functional Diagram © 2000 National Semiconductor Corporation Features n Operates from n Less than 10 µs acquisition time n TTL, PMOS, CMOS compatible logic input n 0 ...

Page 2

... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Power Dissipation (Package Limitation) (Note 2) Operating Ambient Temperature Range LF198/LF198A LF298 LF398/LF398A Storage Temperature Range Input Voltage Logic To Logic Reference ...

Page 3

Electrical Characteristics The following specifcations apply for − LOGIC REFERENCE = 0V, LOGIC HIGH = 2.5V, LOGIC LOW = 0V unless otherwise specified. L Parameter Input Impedance T Gain Error T Full Temperature Range Feedthrough ...

Page 4

Typical Performance Characteristics Output Droop Rate DS005692-20 Leakage Current into Hold Capacitor DS005692-23 Power Supply Rejection DS005692-26 Note 10: See Definition www.national.com (Continued) Hold Step DS005692-21 Phase and Gain (Input to Output, Small Signal) DS005692-24 Output Short Circuit Current DS005692-27 ...

Page 5

Typical Performance Characteristics Input Bias Current DS005692-29 Output Transient at Start of Sample Mode Logic Input Configurations DS005692-33 Threshold = 1.4V (Continued) Feedthrough Rejection Ratio (Hold Mode) DS005692-30 Output Transient at Start of Hold Mode DS005692-12 TTL & CMOS 3V ...

Page 6

Logic Input Configurations + Threshold = 0 1.4V Threshold +4V Application Hints Hold Capacitor Hold step, acquisition time, and droop rate are the major trade-offs in the selection of a hold capacitor value. Size and cost may ...

Page 7

Application Hints (Continued) logic input for signal delay, calculate the slope of the wave- form at the threshold point to ensure that least 1.0 V/µs. Sampling Dynamic Signals Sample error to moving input signals probably causes more ...

Page 8

Typical Applications X1000 Sample & Hold * For lower gains, the LM108 must be frequency compensated Ramp Generator with Variable Reset Level www.national.com V OUT DS005692-39 Integrator with Programmable Reset Level DS005692-42 8 Sample and Difference Circuit (Output Follows Input ...

Page 9

Typical Applications (Continued) Output Holds at Average of Sampled Input Reset Stabilized Amplifier (Gain of 1000) DS005692-46 Fast Acquisition, Low Droop Sample & Hold DS005692-49 9 Increased Slew Current DS005692-47 DS005692-50 www.national.com ...

Page 10

Typical Applications (Continued) Synchronous Correlator for Recovering Signals Below Noise Level DC & AC Zeroing www.national.com DS005692-52 Staircase Generator DS005692-59 * Select for step height 50k 1V Step 10 2–Channel Switch DS005692- ± ± Gain 1 0.02% 1 ...

Page 11

... Aperture Time: The delay required between “Hold” com- mand and an input analog transition, so that the transition does not affect the held output. Small-Outline Package DS005692-15 Order Number LF298M or LF398M See NS Package Number M14A 11 DS005692-56 Metal Can Package DS005692-14 ...

Page 12

... Physical Dimensions Order Number LF198H, LF298H, LF398H, LF198AH or LF398AH www.national.com inches (millimeters) unless otherwise noted Metal Can Package (H) NS Package Number H08C Molded Small-Outline Package (M) Order Number LF298M or LF398M NS Package Number M14A 12 ...

Page 13

... NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant ...

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