Question about the TDA2009A maximum input voltage

Discussion in 'The Projects Forum' started by cumesoftware, Oct 2, 2009.

  1. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
    1,330
    10
    I'm building an amplifier from scratch directly based on the circuit for stereo as suggested in the TDA2009A, from ST. My question is related with the input voltage. It says in the datasheet that the input saturation voltage is 300mV.

    My question is, is the input saturation voltage dependent from the gain and supply voltage and has to do with the overall amplifier saturation, or it is independent from any of those factors and has to do with the fact that the input transistors might saturate if this value is overlooked?
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Its datasheet shows a 24V supply so its max output is about 7V RMS. It is 12V RMS when bridged.
    Its datasheet shows a gain of 64 and a gain of 100.

    If you use the gain of only 64 then when the output is clipping (7V RMS) then the input is only 109mV RMS which is far from input saturation.
     
  3. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
    1,330
    10
    So the figure refers only to the saturation of the input transistors, right?
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    If you set the gain to what they recommend, the output transistors will have severe clipping distortion before the input transistors saturate.
    But if you reduce the gain then the input transistors might have severe saturation distortion and maybe the IC will oscillate.
     
  5. cumesoftware

    Thread Starter Senior Member

    Apr 27, 2007
    1,330
    10
    Thanks for your help!
     
Loading...