SLPS814 November   2025 RES21A-Q1

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
    6. 5.6 Typical Characteristics
  7. 6 Parameter Measurement Information
    1. 6.1 DC Measurement Configurations
    2. 6.2 AC Measurement Configurations
    3. 6.3 Error Notation and Units
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Ratiometric Matching for Low Gain Error
        1. 7.3.1.1 Absolute and Ratiometric Tolerances
      2. 7.3.2 Ratiometric Drift
      3. 7.3.3 Long-Term Stability
      4. 7.3.4 Humidity Resilience
      5. 7.3.5 Ultra-Low Noise
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Amplifier Feedback Circuit
        1. 8.1.1.1 Amplifier Feedback Circuit Example
      2. 8.1.2 Voltage Divider Circuit
        1. 8.1.2.1 Voltage Divider Circuit Example
        2. 8.1.2.2 Voltage-Divider Circuit Drift
      3. 8.1.3 Discrete Difference Amplifier
        1. 8.1.3.1 Difference-Amplifier Common-Mode Rejection Analysis
        2. 8.1.3.2 Difference-Amplifier Gain Error Analysis
      4. 8.1.4 Discrete Instrumentation Amplifiers
      5. 8.1.5 Fully Differential Amplifier
      6. 8.1.6 Unconventional Circuits
        1. 8.1.6.1 Single-Channel Voltage Divider
        2. 8.1.6.2 Single-Channel Amplifier Gain
          1. 8.1.6.2.1 Gain Scaling the RES60A-Q1 With the RES21A-Q1
        3. 8.1.6.3 Unconventional Instrumentation Amplifiers
    2. 8.2 Typical Application
      1. 8.2.1 Common-Mode Shifting Input Stage
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Examples
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 PSpice® for TI
        2. 9.1.1.2 TINA-TI™ Simulation Software (Free Download)
        3. 9.1.1.3 TI Reference Designs
        4. 9.1.1.4 Analog Filter Designer
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.1.6.2 Single-Channel Amplifier Gain

The RES21A-Q1 is often used to implement the feedback network of an amplifier and set the circuit gain, as discussed in Section 8.1.1. Typically, RG and RIN act as RX and RY respectively (or vice versa) in this circuit, and dividers 1 and 2 are arranged as two independent channels. If, however, unconventional values of GInv or GNoninv are required, combining the four resistors of a single RES21A-Q1 in various series and parallel combinations achieves this requirement, but at the expense of a reduction in channel count. The following tables showcase some of the permutations of possible RES21A-Q1 connections, and report the GInv transfer function associated with each. To calculate GNoninv for each scenario, simply add 1 to the magnitude of the given GInv.

Table 8-6 Effective Transfer Function GInv for Some RES21A-Q1 Resistor Permutations, Adjusting RY
RX RIN RIN1 RIN1 RIN1 RG RG1 RG1 RG1
RY RG RG1 + RIN2 RG1 + RG2 RG1 + RG2 + RIN2 RIN RIN1 + RIN2 RIN1 + RG2 RIN1 + RG2 + RIN2
GR21 EFFECTIVE TRANSFER FUNCTION GInv
1 1 0.5 0.5 0.3333 1 0.5 0.5 0.3333
1.5 0.6667 0.4 0.3333 0.25 1.5 0.75 0.6 0.4286
1.6667 0.6 0.375 0.3 0.2308 1.6667 0.8333 0.625 0.4545
2 0.5 0.3333 0.25 0.2 2 1 0.6667 0.5
2.5 0.4 0.2857 0.2 0.1667 2.5 1.25 0.7143 0.5556
3 0.3333 0.25 0.1667 0.1429 3 1.5 0.75 0.6
4 0.25 0.2 0.125 0.1111 4 2 0.8 0.6667
5 0.2 0.1667 0.1 0.0909 5 2.5 0.8333 0.7143
9 0.1111 0.1 0.0556 0.0526 9 4.5 0.9 0.8182
10 0.1 0.0909 0.05 0.0476 10 5 0.9091 0.8333
Table 8-7 Effective Transfer Function GInv for Some RES21A-Q1 Resistor Permutations, Adjusting RX
RX RG RG1 + RIN2 RG1 + RG2 RG1 + RG2 + RIN2 RIN RIN1 + RIN2 RIN1 + RG2 RIN1 + RG2 + RIN2
RY RIN RIN1 RIN1 RIN1 RG RG1 RG1 RG1
GR21 EFFECTIVE TRANSFER FUNCTION GInv
1 1 2 2 3 1 2 2 3
1.5 1.5 2.5 3 4 0.6667 1.3333 1.6667 2.3333
1.6667 1.6667 2.6667 3.3333 4.3333 0.6 1.2 1.6 2.2
2 2 3 4 5 0.5 1 1.5 2
2.5 2.5 3.5 5 6 0.4 0.8 1.4 1.8
3 3 4 6 7 0.3333 0.6667 1.3333 1.6667
4 4 5 8 9 0.25 0.5 1.25 1.5
5 5 6 10 11 0.2 0.4 1.2 1.4
9 9 10 18 19 0.1111 0.2222 1.1111 1.2222
10 10 11 20 21 0.1 0.2 1.1 1.2

For example, consider an inverting amplifier circuit constructed with RX = RG1 + RG2 and RY = RIN1. Using a RES21A00-Q1 device with Gnom = 10 for this implementation gives an effective transfer function GINV = RX / RY = (100kΩ + 100kΩ) / 10kΩ = 200kΩ / 10kΩ = 20. Therefore, VOUT = –VIN × GINV = VIN × –20.

RES21A-Q1 VOUT = –20 × VIN, Effective CircuitFigure 8-12 VOUT = –20 × VIN, Effective Circuit
RES21A-Q1 VOUT = –20 × VIN, Implemented With RES21A00-Q1 Figure 8-13 VOUT = –20 × VIN, Implemented With RES21A00-Q1