SBOS867C August   2017  – October 2023 OPA838

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics: VS = 5 V
    6. 7.6 Electrical Characteristics: VS = 3 V
    7. 7.7 Typical Characteristics: VS = 5 V
    8. 7.8 Typical Characteristics: VS = 3 V
    9. 7.9 Typical Characteristics: Over Supply Range
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Common-Mode Voltage Range
      2. 8.3.2 Output Voltage Range
      3. 8.3.3 Power-Down Operation
      4. 8.3.4 Trade-Offs in Selecting The Feedback Resistor Value
      5. 8.3.5 Driving Capacitive Loads
    4. 8.4 Device Functional Modes
      1. 8.4.1 Split-Supply Operation (±1.35 V to ±2.7 V)
      2. 8.4.2 Single-Supply Operation (2.7 V to 5.4 V)
      3. 8.4.3 Power Shutdown Operation
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Noninverting Amplifier
      2. 9.1.2 Inverting Amplifier
      3. 9.1.3 Output DC Error Calculations
      4. 9.1.4 Output Noise Calculations
    2. 9.2 Typical Applications
      1. 9.2.1 High-Gain Differential I/O Designs
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Transimpedance Amplifier
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curve
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 TINA-TI™ Simulation Model Features
    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
  12.   Mechanical, Packaging, and Orderable Information

Package Options

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

9.1.1 Noninverting Amplifier

The OPA838 can be used as noninverting amplifier with signal input to the noninverting input (VIN+). Figure 8-1 illustrates a basic block diagram of the circuit. VREF is often ground when split supplies are used.

If VIN = VREF + VSIG, and the gain setting resistor (RG) is dc referenced to VREF, use Equation 1 to calculate the output of the amplifier.

Equation 1. GUID-9A43B37B-E1D3-480A-8672-59075534B5CB-low.gif

The noninverting signal gain (also called the noise gain) of the circuit is set by: GUID-8A1601CE-F5CD-4E2A-99B7-6F1454F7D5F3-low.gif

VREF provides a reference around which the input and output signals swing. Output signals are in-phase with the input signals within the flat portion of the frequency response. For a high-speed, low-noise device like the OPA838, the values selected for RF (and the RG for the desired gain) can strongly influence the operation of the circuit. For the characteristic curves, the noninverting circuit of Figure 9-1 shows the test configuration. Table 9-1 lists the recommended resistor values over gain.

GUID-165D1AC3-88E6-42C9-8CB6-DA21AB63A11B-low.gifFigure 9-1 Noninverting Characterization Circuit

Table 9-1 lists the recommended resistor values from target gains of 6 V/V to 20 V/V. This table controls the RF and RG values to set the resistor noise contribution at approximately 40% of the total output noise power. This increases the spot noise at the output over what the op amp voltage noise produces by 20%. Lower values reduce the output noise of any design at the cost of more power in the feedback circuit. Using the TINA model and simulation tool shows the impact of different resistor value choices on response shape and noise.

Table 9-1 Noninverting Recommended Resistor Values
TARGET AVERAGE RF (Ω) RG (Ω) ACTUAL GAIN (V/V) GAIN (dB)
6 1000 200 6 15.56
7 1180 196 7.02 16.93
8 1370 196 7.99 18.05
9 1540 191 9.06 19.15
10 1690 187 10.04 20.03
11 1870 187 11 20.83
12 2050 187 11.96 21.56
13 2210 182 13.14 22.37
14 2370 182 14.02 22.94
15 2550 182 15.01 23.53
16 2740 182 16.05 24.11
17 2870 178 17.12 24.67
18 3090 182 17.98 25.09
19 3240 178 19.20 25.67
20 3400 178 20.1 26.06
21 3570 178 21.06 26.47