This circuit is from a 1977 Radio Shack manual. The photocell is an LDR and the operational one is a 741. Components with non-standard values can be approximated.
Using an operational and a transistor according to the maximum desired current, this circuit...
In this circuit R1 has 2M5, R2 and R3 are 5M obtaining a detection current for the diode of 0.5...
Found in 1966 General Electric documentation, this circuit uses solicon unilateral switches (SUS)...