SNOSDB6D December   2020  – October 2024 LMP7704-SP

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics VS = 5 V
    6. 5.6 Electrical Characteristics VS = 10 V
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Radiation Hardened Performance
      2. 6.3.2 Engineering Model (Devices With /EM Suffix)
      3. 6.3.3 Diodes Between the Inputs
      4. 6.3.4 Capacitive Load
      5. 6.3.5 Input Capacitance
    4. 6.4 Device Functional Modes
      1. 6.4.1 Precision Current Source
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Low Input Voltage Noise
      2. 7.1.2 Total Noise Contribution
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.4.1 Precision Current Source

The LMP7704-SP can be used as a precision current source in many different applications. Figure 6-6 shows a typical precision current source. This circuit implements a precision, voltage-controlled current source. Amplifier A1 is a differential amplifier that uses the voltage drop across RS as the feedback signal. Amplifier A2 is a buffer that eliminates the error current from the load side of the RS resistor. In general, the circuit is stable as long as the closed-loop bandwidth of amplifier A2 is greater then the closed-loop bandwidth of amplifier A1. If A1 and A2 are the same type of amplifiers, then the feedback around A1 reduces bandwidth compared to A2.

LMP7704-SP Precision Current SourceFigure 6-6 Precision Current Source

The equation for output current is derived as shown in Equation 4:

Equation 4. LMP7704-SP

Solving for current I results in Equation 5:

Equation 5. LMP7704-SP