SNOS631E November   1994  – March 2025 LMC6061 , LMC6062 , LMC6064

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: LMC6061
    5. 5.5 Thermal Information: LMC6062
    6. 5.6 Thermal Information: LMC6064
    7. 5.7 Electrical Characteristics
    8. 5.8 Typical Characteristics
  7. 6Application and Implementation
    1. 6.1 Applications Information
      1. 6.1.1 Amplifier Topology
      2. 6.1.2 Compensating For Input Capacitance
      3. 6.1.3 Capacitive Load Tolerance
      4. 6.1.4 Latchup
    2. 6.2 Typical Applications
      1. 6.2.1 Instrumentation Amplifier
      2. 6.2.2 Low-Leakage Sample-and-Hold
      3. 6.2.3 1Hz Square-Wave Oscillator
    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 Example
  8. 7Device and Documentation Support
    1. 7.1 Receiving Notification of Documentation Updates
    2. 7.2 Support Resources
    3. 7.3 Trademarks
    4. 7.4 Electrostatic Discharge Caution
    5. 7.5 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|14
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, like the LMC606x. Although the LMC606x is highly stable over a wide range of operating conditions, take certain precautions 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 high input impedances are demanded, guarding of the LMC606x is suggested. Guarding input lines can not only reduce leakage, but also lower stray input capacitance. See also Section 6.3.1.1.

The effect of input capacitance can be compensated for by adding a capacitor. Place a capacitor, CF, around the feedback resistor (as in Figure 6-1 ) such 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
LMC6061 LMC6062 LMC6064 Canceling the Effect of Input Capacitance Figure 6-1 Canceling the Effect of Input Capacitance

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