This circuit was suggested by National Semiconductor and is present elsewhere on this site. The LM2575 is not very common today and should be mounted on a heatsink.
This 2003 circuit serves to digitally show the intensity of a sound captured by a microphone....
The circuit shown in the figure makes it possible to control a stepper motor via a PC's serial port...
This circuit was found in an old American documentation. Its purpose is a proportional scanning signal...