Voltage inverter

Here is a circuit that produces a negative voltage from a positive one, for instance, from +5 V to -10 V. The output voltage, Uo, is determined from Uo = -1.2(R, /R2 + 1) [V] As in other, similar circuits, the maxi- mum output current depends on the ratio between input and output voltage and is calculated from Io(max)= 500/(R1 /R2 + 1) [mA] The choke is readily made with a 17.5 mm pot core on which 85 turns of 0.2 mm2enamelled copper wire are close-wound. The maximum input voltage to the IC is 15 V. Efficiency is of the order of voltage inverter 91 60 per cent. (St) ee text