This circuit was found in documentation from the 1980s. The integrated circuit is from the time and the voltage depends on the desired power, and the component's datasheet should be consulted.
This oscillator, with an old operational from the 80's, was found in an American publication of the...
This high current circuit using a MOSFET and an operational one was found in a documentation from...
With this circuit, from Newton C. Braga's Mechatronics Sourcebook it is possible to control up to 5...