This circuit was found in a 90's EDN. The circuit has a well-known configuration. The voltage obtained depends on the number of diodes. Capacitors depend on the desired current.
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
This circuit is from an old operational amplifiers manual. However, the setting applies to modern...
Using an operational amplifier, the figure shows how to convert the waveform to low frequency...