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 circuit was found in the Spanish magazine No longer in existence, Mundo Electrónico, in a...
This circuit that has a response from 10 Hz to 700 kHz was found in Philips documentation from 1968. Dual...
This simple sweep generator circuit has been found in older documentation, but can still be easily...