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I am designing an amplifier. I have a BT_201 Bluetooth module. I sent a 1 kHz test signal and measured it with an oscilloscope. The Bluetooth audio output oscillates on the positive side. I'm using a TDA7293 in my amplifier. It is a class AB. I need to use the Bluetooth output signal on both positive and negative side.

I did research for this, but I could not reach tangible results. In my research, I always found the opposite of what I wanted.

How can I level shift this audio signal? The signal seems to work between 0-5 V, but I need -2.5 V to +2.5 V.

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    \$\begingroup\$ If you have a input capacitor at TDA input, then you don't need to worry about this offset voltage. \$\endgroup\$
    – G36
    Oct 6, 2022 at 18:59
  • \$\begingroup\$ Burak, you probably could not find much because the solution is so so so common (capacitor, to remove the DC) that a lot of time isn't spent on it. I can see why the Bluetooth output might be shifted. Perhaps the output is more commonly used with MCU ADCs that only accept a positive signal. But it is easy to shift. If you place a series cap (Bluetooth output to one pin and then the other pin goes to the input you are feeding) then it will automatically 'charge up' to just the right average voltage to perform the shift. There are reasons why it does. But you can trust that it will. \$\endgroup\$
    – jonk
    Oct 7, 2022 at 0:10
  • \$\begingroup\$ I didn't think the solution would be this simple. I was thinking of solving it using opamp. Thanks for your help. \$\endgroup\$
    – Burak T.
    Oct 7, 2022 at 7:08

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Use a series capacitor to remove the DC offset.

The Typical Application circuit in the datasheet shows capacitors on the input.

If you have an amplifier module using the TDA7293, rather than a bare IC, the module should have the necessary input coupling capacitors so you shouldn't need to add one.

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  • \$\begingroup\$ I didn't think the solution would be this simple. I was thinking of solving it using opamp. Thanks for your help. \$\endgroup\$
    – Burak T.
    Oct 7, 2022 at 7:08

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