TPA2031D1: Input capacitance

Hi, Naizeng,

It is important to understand that this kind of amplifiers require of a DC bias level. This DC bias level is generated by the internal bias circuit + an external capacitor, like the first diagram you showed (single-ended input). Actually, if you measure the connection between the input capacitor and the input pin, you should see this DC bias level.

The second diagram is a differential connection, so all the common voltage will be reduced anyway. Even if you place the input capacitors, this DC bias will be eliminated due to the differential connection. So, the result will be basically the same with or without the capacitors. I would say that the capacitors will be used just for filtering purposes in this case, but they won't affect the normal behavior of the circuit.

I hope this is clear. Please let me know if you have additional questions or comments.

Best regards,
Luis Fernando Rodríguez S.