With the circuit of the figure, we can obtain a voltage of 24V under currents of a few milliamps, maximum, from a 12V source. What we have is an audio oscillator that charges and discharges the 47 nF capacitor, adding its voltage to the input. The frequency can be changed by changing the value of 4n7 to obtain the maximum yield from the voltage modification. The CMOS inverter port can be exchanged for one of the 4 ports of a 4093 connected as an inverter.
