This circuit of a Popular Electronics from the 90s makes use of components of the time. The circuit has sampling and retention capabilities and a conversion rate of 1V / kHz.
The circuit shown in the figure is suggested by Micrel, based on the MIC2570 boost voltage...
This circuit can work with almost any JFET. The circuit is from an Electronics Now from April...
This circuit should only be used with incandescent lamps and the SCR should be fitted with a heat...