Voltage Inverter 2

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.

Schematic
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).

Voltage Inverter

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.

Schematic
Parts

R1 ---- 24K 1/4 Watt Resistor
R2 ---- 56K 1/4 Watt Resistor

C1 ---- 3300pF 25V Ceramic Capacitor
C2 ---- 47uF 25V Electrolytic Capacitor
C3 ---- 10uF 25V Electrolytic Capacitor

D1, D2 ---- 1N4148 Silicon Diode
U1 ---- 555 Timer
MISC ---- Wire, Board

Notes

1. 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.

2. For better regulation, a 79LOxx series regulator can be used.

3. A zener diode may also be used to regualte the output voltage.