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TAS5624A: Disadvantage of Constant Gain design

Bernd Nimmrichter
Prodigy 75 points
Part Number: TAS5624A
Other Parts Discussed in Thread: TAS5352A,

I am wondering why TI is now more and more switching to a constant gain design.

Some comparisons:

With my TAS5352A design i get a Signal to Noise Ratio of 105dB with a 24V powersupply and also 105dB with a 34V powersupply (measured !)..

With the TAS5624A constant gain design i will get  a Signal to Noise Ratio of 102.5dB at 24V powersupply and 105dB with a 36V powersupply.

With a voltage dependent gain design and a class G Powersupply you can easily get an Idle Noise to Fullscale Output Ratio S/N of 110db.

With the TAS5624A you can't. The noise remains the same at every powersupply voltage.

With a TAS5352A design the power output goes down when the powersupply voltage goes down. Its a kind of limiter ! I like this smooth overload behaviour.

Here comes the question:

What is the advantage of Constant Gain design ?

I am very interested to hear what i am missing .

Regards

Bernd

  • 0
    TI__Guru 61920 points

    Bernd,

    While both designs have their merits, constant gain works better in applications where supply voltage can vary and the customer wants a consistent output power. This way if their battery drains or power supply dips momentarily, their audio output remains the same.

    The reason it is this way is because of open loop vs closed loop design. Closed loop is favored because it is easier to protect and more predictable.


    Regards,

    -Adam