SBOSAA5B April   2022  – September 2022 OPA2675

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Family Comparison Table
  6. Pin Configuration and Functions
  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: Full Bias and Offline Mode VS = ±6 V
    6. 7.6  Electrical Characteristics: 75% Bias Mode VS = ±6 V
    7. 7.7  Electrical Characteristics: 50% Bias Mode VS = ±6 V
    8. 7.8  Electrical Characteristics: DIfferential Output  VS = 12 V
    9. 7.9  Electrical Characteristics: VS = 5 V
    10. 7.10 Typical Characteristics: VS = ±6 V, Full Bias
    11. 7.11 Typical Characteristics: VS = ±6 V Differential, Full Bias
    12. 7.12 Typical Characteristics: VS = ±6 V, 75% Bias
    13. 7.13 Typical Characteristics: VS = ±6 V, 50% Bias
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Operating Suggestions
        1. 8.3.1.1 Setting Resistor Values to Optimize Bandwidth
        2. 8.3.1.2 Output Current and Voltage
        3. 8.3.1.3 Driving Capacitive Loads
        4. 8.3.1.4 Line Driver Headroom Model
        5. 8.3.1.5 Noise Performance
    4. 8.4 Device Functional Modes
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 High-Speed Active Filters
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Thermal Analysis
    2. 10.2 Input and ESD Protection
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Setting Resistor Values to Optimize Bandwidth

A current-feedback op amp such as the OPA2675 can hold an almost constant bandwidth over signal gain settings with the proper adjustment of the external resistor values, which are shown in the Typical Characteristics; the small-signal bandwidth decreases only slightly with increasing gain. These characteristic curves also show that the feedback resistor is changed for each gain setting. The absolute values of RF on the inverting side of the circuit for a current-feedback op-amp can be treated as a frequency response compensation element, whereas the ratios of RF and RG set the signal gain.

Figure 8-2 shows the small-signal frequency response analysis circuit for the OPA2675.

GUID-DF333E99-54A7-4EF8-891D-731F36F49B25-low.gifFigure 8-2 Current-Feedback Transfer Function Analysis Circuit
GUID-9F9CD090-AE27-43E7-A183-52FDDC157F38-low.gifFigure 8-3 Feedback Resistor Versus Noise Gain

The key elements of this current-feedback op amp model are:

α = buffer gain from the noninverting input to the inverting input

RI = buffer output impedance

IERR = feedback error current signal

Z(s) = frequency-dependent open-loop transimpedance gain from IERR to VO

Equation 1. GUID-99BF9684-7C4B-4132-A00F-F88FFFBB52ED-low.gif

A current-feedback op amp senses an error current in the inverting node (as opposed to a differential input error voltage for a voltage-feedback op amp) and passes this on to the output through an internal frequency-dependent transimpedance gain. The Typical Characteristics show this open-loop transimpedance response, which is analogous to the open-loop voltage gain curve for a voltage-feedback op amp. Refer to the training videos shown in TI Precision Labs for further understanding on the CFA operating theory.

The values for RF versus gain shown in Figure 8-3 are approximately equal to the values used to generate the Typical Characteristics and give a good starting point for designs where bandwidth optimization is desired.