SLPS732B june   2021  – april 2023 JFE150

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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
    6. 6.6 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 AC Measurement Configurations
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Ultra-Low Noise
      2. 8.3.2 Low Gate Current
      3. 8.3.3 Input Protection
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Input Protection Diodes
      2. 9.1.2 Capacitive Transducer Input Stage
      3. 9.1.3 Common-Source Amplifier
      4. 9.1.4 Composite Amplifiers
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
        1. 10.1.1.1 PSpice® for TI
        2. 10.1.1.2 TINA-TI™ Simulation Software (Free Download)
        3. 10.1.1.3 TI Reference Designs
        4. 10.1.1.4 Filter Design Tool
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.2 Detailed Design Procedure

This design provides 60 dB of gain with extremely high input impedance at a very low frequency response. The order of design priorities are as follows:

  • The JFE150 bias current is set by selecting the desired bias current and noise tradeoff (see Figure 6-11). The input-referred noise is dominated by the JFE150 bias current and gain. To set the bias current point, adjust the source resistance according to Figure 9-3.
  • After the bias current is selected, set the JFET stage gain as high as possible without pushing the device into the linear region of operation. This is achieved by using the largest drain resistor (RD) possible while maintaining a minimum of 2 V across the drain to source nodes. Be aware that the amplifier forces the drain node to match the noninverting amplifier input in normal closed-loop operation. Both ac and dc voltages must be considered, but generally, only the dc operating point on the drain is considered because the ac voltage swing is minimal.
  • Set the closed gain according to RF2 and RS2, as seen in Equation 4. Thermal noise from RS2 directly couples into the circuit; therefore, small values for this resistor are required.
  • CS is required to block dc voltages from altering the bias point set by source resistor RS. CS also forms the low-frequency response as described in Equation 5.