This simple circuit can work with either 4.5 V or 6 or 9 V if a 1k resistor is added in series with the set of LEDs. The circuit is from an old French publication.
This control circuit up to 1 kW was found in a 1967 RCA documentation. The components are from...
We found this circuit in an Analog Devices documentation from the 1990s. It provides an...
In this circuit the signal from the phototransistor is amplified by a Darlington stage and then...