This circuit was found in an Electronics World of 1968. It can be applied to any modern triac and the diac can be any type. The load depends on the triac.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
The adjustment of the maximum load voltage is made in the trimpot. The circuit is from 1994...
In the figure we have the conventional configuration of a differential amplifier with the...