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 from the 70's used germanium transistors and operated in the range of medium and...
The figure shows how to convert a rectangular signal into a triangular signal using an integrator. The...
This circuit was found in a National Semiconductor manual from the 1970s, appearing in articles and on...