We found this circuit on a Radio Electronics. Similar configurations can be found in this section. The operational amplifier can be of almost any type.
April 2017 - The new Maxim Integrated MAX20733 and 20745 switched regulators are available from...
The indicator for this circuit is a mini buzzer with a 1.5 V oscillator. The circuit can also be...
This 80's documentation circuit includes an amplifier of the era. Used integrated circuits are...