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LM4950: Questions regarding LM4950 speaker load

Robert Alfred Kecs
Prodigy 170 points

Part Number: LM4950

Hi,

I am writeing in regards to the LM4950 Class AB audio amplifier.

I want to use a 4 OHM speaker in BTL configuration. In all examples such loads are single ended.

Is is possivle to use 4 OHM in BTL and potencialy not use the largest gain setting?

The reason why i want to use BTL is so that i would get lower distorsions useing the same available power rails. 

If needed i can also add some series resistors. 

Bestreagrds,

Robert

  • 0
    TI__Guru** 114565 points

    Hi Robert,

    There is load impedance limitation due to current and thermal characteristics of the amplifier. Some information about this is mentioned in the Power Dissipation section in data sheet page 17.

    In order to use 4Ohm speakers in BTL mode, you may add resistor in series, so the total load increases to 8Ohm at least. Also, if you're not using the full power output from the amplifier you can try using the 4Ohm directly, although you have to test thoroughly to verify there are no current or thermal related issues.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 170 points

    Hi Ivan,

    THX for your time, i was considering a heatsink anyway and max gain was mostly for edge cases with low on time.

    From what i read i will be ok if i test it first.

    Best regards,

    Robert