This circuit from a Popular Electronics from the 90s uses a common optocoupler and a general-purpose transistor to control a sensitive relay that can be from 6 to 12 V.
This circuit was found in an old American magazine for radio amateurs. The circuit is based on a...
The LDO series (Low Dropout) TPS80 from Texas Instruments (www.ti.com) can provide output voltages...
This circuit is from Motorola's 1990 Linear Databook. We can implement it with other operational...