SNOS674G November   1997  – April 2020 LMC6482

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Rail-to-Rail Input
      2.      Rail-to-Rail Output
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics for V+ = 5 V
    6. 6.6 Electrical Characteristics for V+ = 3 V
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Amplifier Topology
      2. 7.3.2 Input Common-Mode Voltage Range
      3. 7.3.3 Rail-to-Rail Output
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Upgrading Applications
      2. 8.1.2 Data Acquisition Systems
      3. 8.1.3 Instrumentation Circuits
      4. 8.1.4 Spice Macromodel
    2. 8.2 Typical Applications
      1. 8.2.1 3-V Single-Supply Buffer Circuit
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Capacitive Load Compensation
          2. 8.2.1.2.2 Capacitive Load Tolerance
          3. 8.2.1.2.3 Compensating For Input Capacitance
          4. 8.2.1.2.4 Offset Voltage Adjustment
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Typical Single-Supply Applications
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Compensating For Input Capacitance

It is quite common to use large values of feedback resistance with amplifiers that have ultra-low input current, like the LMC6482. Large feedback resistors can react with small values of input capacitance due to transducers, photo diodes, and circuits board parasitics to reduce phase margins.

LMC6482 01171319.pngFigure 64. Canceling the Effect of Input Capacitance

The effect of input capacitance can be compensated for by adding a feedback capacitor. The feedback capacitor (as in Figure 64), Cf, is first estimated by:

Equation 1. LMC6482 01171392.png

or

Equation 2. R1 CIN ≤ R2 Cf

which typically provides significant overcompensation.

Printed-circuit-board stray capacitance may be larger or smaller than that of a bread-board, so the actual optimum value for Cf may be different. The values of Cf should be checked on the actual circuit. (Refer to the LMC660 quad CMOS amplifier data sheet for a more detailed discussion.)