Obtained in a 1968 Electronics World, this circuit uses transistors from the time and the sensor is a common LDR. The component values are for scales from 0.01 to 100 foot-candle.
This circuit uses an unusual operational amplifier nowadays and has a very low consumption. The...
This is a traditional inverter amplifier configuration with voltage gain 10. The operational...
Both the operational amplifier and the diodes admit equivalents in this circuit suggested by...