I'm wondering if it is possible to get three voltages out of two voltage regulators. Let's say I have a 9V and a 12V regulator in a circuit. Would I be able to get the 4 voltages below out of this setup (if I include the input)?

  1. 24V input
  2. 9V out
  3. 12V out; and
  4. 3V (difference between the 9V and 12V)

I can not see why this won't work.

  • \$\begingroup\$ Only works if the nett output current of the regulators is positive. Most voltage regulators cannot sink current. \$\endgroup\$
    – jippie
    Sep 11, 2015 at 16:47

1 Answer 1


Regulators normally do not like to sink current.

If you connect a load between the 12V regulator and the 9V regulator, then the 9V output will tend to rise out of regulation (to as high as 12V for a heavy load). If a load (to ground) on the 9V regulator can be counted on to always be sufficient, then it may work in some limited situations \$^1\$.

It's not really an 'output' though, as it's not referred to ground.

  1. For example, if you put a bypass capacitor between the 12V and 9V outputs then (even with a sufficient steady state load on the 9V output) the 9V output will tend to spike up towards 12V when power is first applied. That could damage something connected to the 9V output.
  • \$\begingroup\$ So if I get special kinds of regulators this is possible? \$\endgroup\$
    – Dave P
    Sep 11, 2015 at 17:33
  • \$\begingroup\$ Possible, but rarely will it be useful. \$\endgroup\$ Sep 11, 2015 at 17:36

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