I found tis circuit in na old documentation from 1958. The circuit uses germanium transistor availble that time and hard to obtain today. The circuit is indicated for phono applications using variable reluctance transducer.
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...