This configuration can be found in several articles on this site. The one shown in the diagram is from the datasheet of the LM101 series amplifiers, but it can be implemented with other types.
This is the single-sourced version of the previous oscillator. Frequency can be changed by...
This is a commercial circuit found in Radio Electronics magazine from September 1960. The circuit has...
This circuit is from a 1998 Poptronics. The circuit triggers a buzzer after a certain time, waking...