The HV2405E integrated circuit is not very common these days. This circuit was found in the August 1998 issue of Electronics Now magazine. The current is a few tens of milliamps.
This circuit appears elsewhere on this site, but from different sources. Using the LM3900, we find this...
This interesting source or isolation transformer also allows to vary the output voltage by...
In this circuit the CA3140, an operational amplifier, is used as a comparator with the zener diode...