This is an interesting configuration of the LM317 voltage regulator found in an EDN from the 90s. The circuit uses an optical coupler and is intended to supply constant current to a sensor resistor.
This small inverter that produces high voltage from a 6 V source was found in an American...
This circuit uses a lower frequency crystal in an excitation system for an oscillator with a coil...
This circuit was obtained from a 1966 magazine but can be easily assembled using the 2N2646 as a...