SBOS293I December   2003  – October 2024 OPA695

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, OPA695ID, OPA695IDBV
    6. 5.6  Electrical Characteristics VS = 5 V, OPA695ID, OPA695IDBV
    7. 5.7  Electrical Characteristics VS = ±5 V, OPA695IDGK
    8. 5.8  Electrical Characteristics VS = 5 V, OPA695IDGK
    9. 5.9  Typical Characteristics: VS = ±5 V, OPA695IDBV, OPA695ID
    10. 5.10 Typical Characteristics: VS = 5 V, OPA695IDBV, OPA695ID
    11. 5.11 Typical Characteristics: VS = ±5 V, OPA695IDGK
    12. 5.12 Typical Characteristics: VS = 5 V, OPA695IDGK
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Wideband Current-Feedback Operation
      2. 6.3.2 Input and ESD Protection
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Operating Suggestions
        1. 7.1.1.1 Setting Resistor Values to Optimize Bandwidth
        2. 7.1.1.2 Output Current and Voltage
        3. 7.1.1.3 Driving Capacitive Loads
        4. 7.1.1.4 Distortion Performance
        5. 7.1.1.5 Noise Performance
        6. 7.1.1.6 Thermal Analysis
      2. 7.1.2 LO Buffer Amplifier
      3. 7.1.3 Wideband Cable Driving Applications
        1. 7.1.3.1 Cable Modem Return Path Driver
        2. 7.1.3.2 Arbitrary Waveform Driver
      4. 7.1.4 Differential I/O Applications
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
        1. 7.2.1.1 Saw Filter Buffer
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curve
    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 Device Support
      1. 8.1.1 Design-In Tools
        1. 8.1.1.1 Demonstration Fixtures
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

7.1.1.5 Noise Performance

The OPA695 offers an excellent balance between voltage and current noise terms to achieve low output noise. The inverting current noise (22 pA/√Hz) is lower than most other current-feedback operational amplifiers, while the input voltage noise (1.8 nV/√Hz) is lower than any unity-gain stable, wideband, voltage-feedback operational amplifier. This low-input voltage noise was achieved at the price of a higher noninverting input current noise (18 pA/√Hz). As long as the ac source impedance looking out of the noninverting node is less than 50 Ω, this current noise does not contribute significantly to the total output noise. The operational amplifier input voltage noise and the two input current noise terms combine to give low output noise under a wide variety of operating conditions. Figure 7-4 shows the operational amplifier noise analysis model with all the noise terms included. In this model, all noise terms are taken to be noise voltage or current density terms in either nV/√Hz or pA/√Hz.

OPA695 Operational Amplifier Noise Figure Analysis Model Figure 7-4 Operational Amplifier Noise Figure Analysis Model

The total output spot-noise voltage can be computed as the square root of the sum of all squared output noise voltage contributors. Equation 1 shows the general form for the output noise voltage using the terms shown in Figure 7-8.

Equation 1. OPA695

Dividing this expression by the noise gain (NG = (1 + RF/RG)) gives the equivalent input referred spot-noise voltage at the noninverting input, as shown in Equation 2:

Equation 2. OPA695

Evaluating these two equations for the OPA695 circuit and component values shown in Figure 6-1 gives a total output spot-noise voltage of 18.7 nV/√Hz and a total equivalent input spot-noise voltage of 2.3 nV/√Hz. This total input referred spot-noise voltage is higher than the 1.8-nV/√Hz specification for the operational amplifier voltage noise alone. This reflects the noise added to the output by the inverting current noise times the feedback resistor. If the feedback resistor is reduced in high-gain configurations (as suggested previously), the total input referred voltage noise given by Equation 2 just approaches the 1.8 nV/√Hz of the operational amplifier. For example, going to a gain of +20 (using RF = 200 Ω) gives a total input referred noise of 2.0 nV/√Hz.

For a more complete discussion of operational amplifier noise calculation, see the Noise Analysis for High Speed Op Amps application note, available through www.ti.com.