How to build Voltage Inverter II

This simple and inexpensive circuit can produce a dual (positive and negative) voltage from a single supply input. It is therefore extremely useful for powering opamp and other circuits that require a dual voltage from a single battery. The circuit will operate at an input voltage from around 5V to 20V and produce a output from +-2.5V to +-10V.

Circuit diagram

Parts
R1 1M Linear Pot
C1,C2 15uf 25V Electrolytic Capacitor
U1 LM380 Audio Amp Chip
MISC Heatsink For U1, Binding Posts (For Input/Output), Wire, Board

Notes
1. U1 dissipates around 1W and will therefore require a heatsink.
2. R1 is used to equalize the outputs. The first time you use the circuit, it should be set to mid range and then adjusted with the aid of a voltmeter. Measure each output while adjusting. The circuit is calibrated when both outputs read the same voltage (either positive or negative).