SNOS611F July   1999  – March 2025 LMC6041 , LMC6042 , LMC6044

PRODUCTION DATA  

  1.   1
  2. 1Features
  3. 2Applications
  4. 3Description
  5. 4Pin Configuration and Functions
  6. 5Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information: LMC6041
    5. 5.5 Thermal Information: LMC6042
    6. 5.6 Thermal Information: LMC6044
    7. 5.7 Electrical Characteristics
    8. 5.8 Typical Characteristics
  7. 6Application and Implementation
    1. 6.1 Application Information
      1. 6.1.1 Amplifier Topology
      2. 6.1.2 Compensating For Input Capacitance
      3. 6.1.3 Capacitive-Load Tolerance
    2. 6.2 Typical Applications
      1. 6.2.1 Instrumentation Amplifiers
      2. 6.2.2 Low-Leakage Sample and Hold
      3. 6.2.3 Square-Wave Generator
      4. 6.2.4 AC Coupled Power Amplifier
    3. 6.3 Layout
      1. 6.3.1 Layout Guidelines
        1. 6.3.1.1 Printed-Circuit-Board Layout for High-Impedance Work
      2. 6.3.2 Layout Examples
  8. 7Device and Documentation Support
    1. 7.1 Receiving Notification of Documentation Updates
    2. 7.2 Support Resources
    3.     Trademarks
    4. 7.3 Electrostatic Discharge Caution
    5. 7.4 Glossary
  9. 8Revision History
  10. 9Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
  • P|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6.1.2 Compensating For Input Capacitance

Large values of feedback resistance are quite common for amplifiers with ultra-low input current, such as the LMC604x.

Although the LMC604x are highly stable over a wide range of operating conditions, certain precautions must be taken to achieve the desired pulse response when a large feedback resistor is used. Large feedback resistors and even small values of input capacitance, due to transducers, photodiodes, and circuit board parasitics, reduce phase margins.

When a high input impedance is demanded, guard the inputs of the LMC604x. Guarding input lines can not only reduce leakage, but lower stray input capacitance as well (see Section 6.3.1.1).

LMC6041 LMC6042 LMC6044 Canceling the Effect of Input Capacitance Figure 6-1 Canceling the Effect of Input Capacitance

Compensate for the effect of input capacitance by adding a capacitor. Place a capacitor, CF, around the feedback resistor (as in Figure 6-1 ) so that:

Equation 1. 1 2 π R 1 C I N ≥ 1 2 π R 2 C F

where

Equation 2. R 1 C I N ≤ R 2 C F

The exact value of CIN is often difficult to know, but CF can be experimentally adjusted so that the desired pulse response is achieved. See the LMC660 and LMC662 for a more detailed discussion on compensating for input capacitance.