This circuit is from Motorola documentation, but can be implemented with virtually any phototransistor and any general-purpose transistor. The supply voltage can also be changed.
This circuit was found in the Spanish magazine No longer in existence, Mundo Electrónico, in a...
This interesting circuit was obtained from a 90's EDN. What it does is generate negative voltages...
This step-down converter with 10 to 60 V input produces a 5 V output with a maximum current of 5...