This 1970s RCA circuit can be triggered by light or dark, depending on how the LDR is connected. The controlled load depends on the triac.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...