This circuit is from American documentation from the 1980s. The circuit can make use of any common NPN transistor and the power comes from two small batteries.
The operational amplifier used in this application is not the most common today. The circuit is...
In the figure we have the way to trigger a 7555 CMOS monostable with a positive pulse. The time...
This circuit was found in a 1926 German publication. It is a crystal or galena (D) receiver. The...