Found in an American documentation from the 90s, this circuit has a configuration that has been extensively explored in other articles on this site. The FET can be the MPF102 or equivalent.
This current meter with many scales was found in a 80s American documentation. The operational amplifier...
This dimmer, from an old publication, can use almost any triac and in shooting a neon lamp. The...
We found this circuit in a 1975 publication. The circuit can be made with more modern equivalent...