LM4836 Confusion About Gain Setting Resistors

Discussion in 'The Projects Forum' started by Sensacell, Oct 30, 2015.

  1. Sensacell

    Thread Starter Well-Known Member

    Jun 19, 2012
    1,132
    267
    I am designing a board that requires a stereo audio amp.
    The LM4836 seems like a nice solution, I took a whack at the design, but it's giving me trouble.

    The outputs are not centered at Vcc/2 as they should be, I think my problem is that I did not close the loop correctly with the feedback resistors connected to the horribly named R_Dock and L_Dock pins? When I read the data sheet again, it talks about calculating the gain: Avd= 2 * (Rf/Ri) but the application schematic never calls out which resistor is which?

    The data sheet is really not really clear about how the input gain is set, and how to bias the input MUX properly.
    I think I need a resistor between the _DOCK pin and the MUX inputs to close the loop and bias the amp correctly?
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    See figure 3 of the data sheet. Ri is the resistor you have. Rf is the resistor you need.

    It is best to cookbook a part you don't understand, meaning start with the sample Circuit before trying any changer.
     
  3. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    In figure 3, Rf is the resistor from LDock to LeftIn (or RDock to RightIn).

    Take ErnieM's advice. Unless you are absolutely sure about the circuit setup, implement it exactly as shown in the figure.
     
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