This is a simple circuit that can be used to convert the positive input voltage become negative voltage. Here’s the figure of the circuit;

Component list:

Part Total Qty. Description

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

D1, D2 2 1N4148 Silicon Diode

U1 1 555 Timer

MISC 1 Wire, Board

In this circuit, 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 79LOxx series regulator can be used. A zener diode may also be used to regulate the output voltage.