This circuit is from Motorola's Linear Interface ICs of 1993. The integrated circuit is not common and the Triac is chosen according to the power of the controlled load.
This circuit was found in a 1982 Maplin documentation. The configuration applies to almost any JFET....
This circuit is a sensor for photodiodes that can be used in optical couplers, encoders and other...
This circuit was found in an American publication from the 60's. The transistor is made of...