This simple circuit is a good solution to the powering a dual supply op
amp from a single battery problem. The circuit simply takes a positive
voltage and inverts it. It uses only one 555 timer and a few other
passive components, so it doesn't add much in the way of size and cost
to a project.

### Parts

R1 | 1 | 24K 1/4 Watt Resistor | |

R2 | 1 | 56K 1/4 Watt Resistor | |

C1 | 1 | 3300pF 25V Ceramic Capacitor | |

C2 | 1 | 47uF 25V Electrolytic Capacitor | |

C3 | 1 | 10uF 25V Electrolytic Capacitor | |

C4 | 1 | 100uF 25V Electrolytic Capacitor | |

D1, D2 | 2 | 1N4148 Silicon Diode | |

U1 | 1 | 555 Timer | |

MISC | 1 | Wire, Board | |

### Notes

- V+ can be anywhere from 4 to 16V. -V is one volt less than V+. So for -12V output, use +13V input. The maximum current output of the circuit is about 280mA, more than enough for a few op amps.
- For better regulation, a 79LO
*xx*series regulator can be used. - A zener diode may also be used to regualte the output voltage.

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