It is quiet easy to obtain drop the voltage either using resistor or regulator but the problem arises when we need to boost the voltage without using inductor and other sophisticated switching mechanism.
The circuit described here is based on 555 timer operated in its monostable multivibrator configuration to generate continuous square wave and switch a pair of PNP and NPN transistor to boost the voltage.
The circuit can be extremely useful in application like switching a 24V relay from 12V supply. This circuit can also be used for powering LED array where the source voltage is less then the forward voltage of the array.
The transistor used in the circuit can be any general purpose NPN and PNP transistor and the value of capacitor C1 and C2 should be 47MFD/25V. Other component values are included in the schematic.

   Schematic

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