There are cases when a higher voltage than an available one has to be derived. If the current happens also to be pretty small, there is a simple circuit which can operate as a voltage doubler, and can be built in extremely low cost.
The voltage doubler uses an astable multivibrator which is based on IC1 (555). This is a rectangular-wave generator operating about 8.7KHz whose output drives T1 and T2. T1 and T2 operate as switches when the output of IC1 is high or low, respectively. When the output of IC1 (pin 3) is low , the negative terminal of C2 is connected to the earth and C2 charges via D1. When pin 3 of IC1 is high, T2 is off, T1 contacts, and C1 is charged to a voltage roughly equivalent to the supply voltage plus the voltage across C2 and D1. During this stage, C2 cannot discharge due to D1.
When powered from 9V, the output voltage is about 15V when a load absorbs a current of about 70mA. The circuit works not only when powered from 9V but also over the whole supply voltage range of the 555. The output is unregulated, which means that the output voltage cannot be kept stable in a wide current range. If a regulated output is required, it is possible to connect an appropriate voltage regulator, but you must take into consideration the power requirements of the regulator.