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I encountered a problem with my TPA2005D1-based audio amplifier circuit. When there is no sound output (0V on the signal input to the amp.), the speaker I am using is getting very hot, in contrast to when I am playing sounds on it, where it only gets warm.

You can find the audio circuit schematic attached below.

In my current PCB, R4 is 0Ohm and C37 is not present, and only the jumper to the AUDIO_DAC net is soldered. Also, the amplifier gain is set to 2 and AUDIO_DAC is the output of the 8-bit DAC pin of an ATtiny1614 microcontroller, which is responsible with generating the audio signal.

The conditions needed for the problem to occur are:

I have no idea why is the speaker getting hot, especially when AUDIO_DAC is 0V. The max. power fed to the speaker should be (0.55 * 2) ^ 2 / 8 = ~0.15W

What is wrong with my schematic? Audio amplifier schematic

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    \$\begingroup\$ What do you measure over the speaker when it gets hot? Is there DC voltage or high frequency AC? \$\endgroup\$
    – Justme
    Aug 18, 2021 at 6:59
  • \$\begingroup\$ What do you want the passband of the input filter to be? I get a corner frequency below 1 kHz. \$\endgroup\$
    – greybeard
    Feb 17, 2023 at 12:11

1 Answer 1

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Your current schematic has two major problems and it does not match anything in the datasheet.

First of all, single ended input should be fed into the negative input via a capacitor, not into the positive input.

However the larger problem is that currently the negative input has no capacitor and it will most likely bias the amplifer to drive DC to speaker.

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