SNOSBI3C July   2000  – October 2018 LF198-N , LF298 , LF398-N

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Connection
      2.      Acquisition Time
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Recommended Operating Conditions
    3. 6.3 Thermal Information
    4. 6.4 Electrical Characteristics, LF198-N and LF298
    5. 6.5 Electrical Characteristics, LF198A-N
    6. 6.6 Electrical Characteristics, LF398-N
    7. 6.7 Electrical Characteristics, LF398A-N (OBSOLETE)
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 TTL and CMOS 3 V ≤ VLOGIC (Hi State) ≤ 7 V
    2. 7.2 CMOS 7 V ≤ VLOGIC (Hi State) ≤ 15 V
    3. 7.3 Operational Amplifier Drive
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Hold Capacitor
      2. 9.1.2 DC and AC Zeroing
      3. 9.1.3 Logic Rise Time
      4. 9.1.4 Sampling Dynamic Signals
      5. 9.1.5 Digital Feedthrough
    2. 9.2 Typical Applications
      1. 9.2.1  X1000 Sample and Hold
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2  Sample and Difference Circuit
      3. 9.2.3  Ramp Generator With Variable Reset Level
      4. 9.2.4  Integrator With Programmable Reset Level
      5. 9.2.5  Output Holds at Average of Sampled Input
      6. 9.2.6  Increased Slew Current
      7. 9.2.7  Reset Stabilized Amplifier
      8. 9.2.8  Fast Acquisition, Low Droop Sample and Hold
      9. 9.2.9  Synchronous Correlator for Recovering Signals Below Noise Level
      10. 9.2.10 2-Channel Switch
      11. 9.2.11 DC and AC Zeroing
      12. 9.2.12 Staircase Generator
      13. 9.2.13 Differential Hold
      14. 9.2.14 Capacitor Hysteresis Compensation
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Device Nomenclature
    2. 12.2 Related Links
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

3 Description

The LFx98x devices are monolithic sample-and-hold circuits that use BI-FET technology to obtain ultrahigh 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 accomplished with a single pin and does not degrade input offset drift. The wide bandwidth allows the LFx98x to be included inside the feedback loop of 1-MHz operational amplifiers without having stability problems. Input impedance of 1010 Ω allows high-source impedances to be used without degrading accuracy.

P-channel junction FETs 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 JFETs have much lower noise than MOS devices used in previous designs and do not exhibit high temperature instabilities. The overall design ensures no feedthrough from input to output in the hold mode, even for input signals equal to the supply voltages.

Logic inputs on the LFx98x are fully differential with low input current, allowing for direct connection to TTL, PMOS, and CMOS. Differential threshold is
1.4 V. The LFx98x will operate from ±5-V to ±18-V supplies.

An A version is available with tightened electrical specifications.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LF298, LF398-N SOIC (14) 8.65 mm × 3.91 mm
LFx98x TO-99 (8) 9.08 mm × 9.08 mm
LF398-N PDIP (8) 9.81 mm × 6.35 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.