The purpose of this circuit is to reduce the ripple of a power supply. The circuit is from a Radio Electronics from March 1985. The transistor must have a capacitance according to the source.
Found with variations on this site, this circuit was taken from an American documentation from the...
This circuit generates damped sounds imitating a drum or other percussion instrument with...
This is the traditional configuration for a limit comparator or window comparator, using two...