The following is a diagram from a DAC datasheet. It's an output stage for a high end audio DAC which has differential outputs.
What would be the best way to implement this when only a single supply voltage is available (say 9v) rather than a dual supply?
Thanks
B
Best Answer
If you only have a single supply, it's very likely that AOUT+ and AOUT- aren't symmetric around 0V, but around some offset voltage V_bias.
That means that you can replace the "ground" in your schematic simply by a virtual ground in the middle between your supply voltage and 0V.
You typically just create such a ground by using relatively low-valued resistors in a voltage divider between Vcc and 0V. The effect of that, however, is that you waste a lot of energy across these.
It's often easier to use a linear voltage regulator (think of the ubiquitous LM78XX regulators) or a fixed voltage reference followed by an opamp in voltage follower config.
The actual voltage of that virtual ground isn't critical – it's just important that it's stable, and you have to realize that what is called "Analog Out" in your circuit is relative to that voltage – so, that virtual ground will be what your speaker will be driven against (i.e. the black cable of the speaker should connect to that, not 0V!).
In other words, there's a lot of drawbacks to doing this.
This is 2016, not 1972. Just grab one of the literally hundreds (TI, Maxim, Analog Devices, ST micro, NXP, ON semi and many, many more) of audio amplifiers designed to work with single supplies and use a schematic from their datasheet or application notes – you'll notice that you can typically find high-valued capacitors at the audio output, which solves the whole bias voltage problem.