This circuit uses a photo-SCR or LASCR that is not a common component today. The relay depends on the load, and the power is supplied by the power grid.
In the figure we show how to implement a voltage reference with the ON Semiconductor rail-to-rail...
This circuit is from a technical documentation from 1978. The maximum output current is of the...
This RF and audio follower applies its signals to a small amplifier. The FET can be any...