>> many analog circuits need both positive and negative supplies

I have a dual output supply but rarely use the negative. It is handy
for op-amps and audio/power amplifiers, but the vast majority of
the time it's on a 'digital' voltage - 3V3, 5V or a battery simulation
voltage. If really necessary it's not difficult to make a negative supply,
albeit probably not tracking, with an SMPS IC
--=20
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