This circuit for a 6.3 V lamp was found in a 1970’s RCA documentation. The circuit applies to any triac and the LDR can be of any type.
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...