This circuit, found in a 1958 magazine, is for reference only, since the components are not easy to find today. The transistors are germanium types and power supply is made by common cells.
This “zero crossing detector” was found in a manual of operational amplifiers from the 1980s....
With this circuit it is possible to follow the transmission in the range of 2 meters with a...
This is another possible version of a negative voltage generator using a 555 integrated circuit. The...