This circuit was found in Siliconix documentation from the 1980s. Equivalent operational amplifiers can be used and the output current is very low.
This oscillator, which can be used as a signal injector, was found in a Popular Electronics from the 90s....
This circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit is based...
This project was published in the April 1989 issue of Radio Electronics magazine. It drives LEDs...