TIDUEW8 August   2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Schematic Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 THS3491 Current Feedback Amplifier Specifications
    3. 2.3 System Design Theory
      1. 2.3.1 Theory of Operation
        1. 2.3.1.1 Concept of Power Supply Range Extension
      2. 2.3.2 Stability Considerations
        1. 2.3.2.1 Inclusion of Series Isolation Resistance (RS)
      3. 2.3.3 Power Dissipation
        1. 2.3.3.1 DC Internal Power Dissipation of Driver Amplifier for a Purely Resistive Output Load
        2. 2.3.3.2 AC Average Internal Power Dissipation of Driver Amplifier for a Purely Resistive Output Load
        3. 2.3.3.3 Internal Average Power Dissipation of Driver Amplifier for RC Output Load
      4. 2.3.4 Thermal Performance
        1. 2.3.4.1 Linear Safe Operating Area (SOA)
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware
    2. 3.2 Test Setup
    3. 3.3 Test Results
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Related Documentation
    1. 5.1 Trademarks

2.3.3.2 AC Average Internal Power Dissipation of Driver Amplifier for a Purely Resistive Output Load

For a continuous sinusoidal output driving a purely resistive load referenced to ground, the internal average power dissipated (POUT(AVG)) in the output transistors of an amplifier can be calculated by integrating the sinusoid for half a cycle and taking the average. Equation 11 uses the positive half-cycle to describe the internal average power dissipation of the driver amplifier when driving a continuous sinusoidal output into a purely resistive ground-referenced load.

Equation 11. P O U T ( A V G ) W =   1 π ∫ 0 π V c c - V O U T V O U T R L   d w t

As VOUT is sinusoidal in this case, it can be defined by Equation 12.

Equation 12. V O U T = V P × S i n ( w t )

where

  • Vp = Peak output voltage swing

In a typical power calculation, the output voltage is the only variable term in the integration, and the remainder of the terms are constant. For the driver amplifier in this design, Vcc is also variable, but because the power supplies are bootstrapped to the output voltage, Vcc can be written simply in terms of the output voltage as in Equation 3. Combining Equation 11, Equation 12, and Equation 3, integrating across the positive half-cycle (0 to π), and dividing by π for averaging, results in Equation 13.

Equation 13. P O U T ( A V G ) W =   V P V S π R L - V P 2 4 R L

Including the quiescent power consumption defined in Equation 6 with Equation 13 produces the total average power dissipation for a single amplifier driving a sinusoid into a purely resistive load, Equation 14.

Equation 14. V S I Q +   V P V S π R L - V P 2 4 R L

Figure 2-10 shows the internal average power dissipation as a function of the peak output voltage (Vp) for various load resistances (RL). The maximum internal average power dissipation occurs when Vp = 2 Vs/π resulting in Equation 15.

Equation 15. P A m p A V G W m a x =   V S I Q +   V S 2 π 2 R L
Figure 2-10 Average Internal AC Power Dissipation of Driver Amplifier