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Question about BTL for TPA3123D2

Justin Reyes
Prodigy 20 points
Other Parts Discussed in Thread: TPA3123D2

Hello!

I have a question regarding the audio input in the TPA3123D2 Class-D Audio Power Amplifier for anyone that has experience with this chip. I currently have the speaker output filters in a Bridge-Tied Load (BTL) configuration using one speaker. What happens if I tie both the left and right audio input pins (LIN and RIN) together, so that they are receiving the same audio signal? Will I hear an amplified signal from the speaker or just no sound at all?

Thanks for your help!

  • 0
    TI__Genius 16645 points

    Hello Justin:

    Since the TPA3123D2 would behave as a  differential input amplifier in BTL mode, if you connect LIN and RIN the output would be the input signal multiplied by the Common Mode Rejection Ratio (CMRR) and this residual multiplied by the gain of the amplifier.  Since this is not a true differential amplifier, you could consider the gain matching to be your CMRR or your residual signal would be ~60dB less than the input signal.

    The residual signal would be multiplied by the gain of the amplifier, 20dB to 32dB; therefore, the output signal would be 28dB to 40dB below the input signal.

    This is all a long way of saying the there would not be very little output signal.

    Regards,

    Fred

  • 0 in reply to Fred Shipley
    Prodigy 20 points

    thanks for the explanation and for your help Fred!