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LME49830 project

Andrés Zappia
Prodigy 135 points

Hi, I am evaluating the performance of a project to 450W bass guitar in 4Ohm and I have some doubts on the choice of amplifier used. For now I think I will use the LME49810 LME49830 instead of as it can handle mosfet and thus would have solved the problem of thermal runaway of the BJT, I would like to know your comments on this choice.

While I'm reading the documentation provided by IT, I would like to know your comments on the output stage, the leaf snaa058a.pdf Figure 2 shows three transistors per side, but in the implementation of Figure 3 shows only two transistors side. How I can define the number of transistors needed to meet the output power I need and maintain safe working area of the transistors?

From already thank you for your support.
regards,
Andrés

  • 0
    TI__Expert 3840 points

    Hi Andres,

    The choice of the LME49810 to drive BJTs versus the LME49830 to drive FETs is purely personal preference. 

    The number of power transistors to use in parallel is dependent upon how conservative you want to be with your design and how hard you think you or your customer may drive the amplifier.  

    From an output current perspective you will need to have enough FETs to drive the required load current; peak or continuous.

    Thermally, as you increase the number of FETs your power dissipation will be divided among them. Depending upon chassis size and heatsink size there may also be limitations here.

    Section 3.1 Output Stage Power Dissipation on page 6 of SNAA058A goes through the thermal aspects relating to the number of transistors.

    Best Regards,

    JD