# dc to split power supply circuits

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#### joshua.svn

##### New Member
hi,

can anyone help me for dc to split power supply circuits.

24 v is the power applied to the circuit and it has to be split to -ve 9v and +ve 9v with respect to
ground. current will be 500mA.

regards
svn.

#### MikeMl

##### Well-Known Member
ps: If the 0V point between +9V and -9V needs to be referenced to the 0V point of the 24V supply, then you will need at least one SMPS.

ps: In the suggestions below, I'm assuming that the 24V supply is floating with respect to the 0V point between the two 9V supplies.

You can use a LM7809 and a LM7909 if both of these are still available. At 1/2A you will need big heatsinks. Or use a positive adjustable regulator like a LM317 and a negative one like a LM337.

Alternately, you could use a single 18V regulator with a power opamp to split the 18V into half. The output of the opamp defines the 0V point between +9V and -9V.

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#### joshua.svn

##### New Member
sorry did not get u?

0 to 24volts , yes we can take +ve voltage , no way we cant use 7909 bcz no o volts with respect to -ve.
svn

#### MikeMl

##### Well-Known Member
sorry did not get u?

0 to 24volts , yes we can take +ve voltage , no way we cant use 7909 bcz no o volts with respect to -ve.
svn
So you need three regulated voltages with respect to a common GND terminal: +24V, +9V, and -9V. Starting from +24V and GND, the only way to get -9V is using an isolated DC to DC converter (SMPS).

Depending on what makes the +24V, you could add a second bridge rectifier (also possibly a second transformer winding) ahead of the original 24V regulator to get a negative voltage.

#### ericgibbs

##### Well-Known Member
sorry did not get u?

0 to 24volts , yes we can take +ve voltage , no way we cant use 7909 bcz no o volts with respect to -ve.
svn
Hi,
Is this what you are asking for ie: +/-9V at 500mA.??

E.

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