Is it possible to create an negative dc signal from a positive dc input signal ?

[Joanito]

Hello all, i was wondering how laptops, smartphones, etc... can create audio signals, since their power supplys are positive dc signals... How can they form the negative part of the audio wave without negative power supply ?

Thanks.

 

[Sergeauckland]

Two ways that a positive only power supply can generate an ac signal without a dc offset. Easiest is just to pass this signal through a capacitor that removes the dc and leaves just the ac.

More complicated is to create a split supply from the positive only supply.

S