This circuit is from a 60's documentation. The capacitance C1 can be between 20 pF and 0.01 uF depending on the generated frequency. Equivalent transistors may be employed.
With this circuit, from a 1991 publication, it is possible to regulate the output of a symmetric source...
This circuit, which appears from other sources on this site, converts a voltage into a current....
For a maximum current of 50 mA the capacitor must be from 470 nF to 250 V if the grid is 110 V and...