This circuit can supply output voltages from 50 to 250 V regulated under a current of 25 mA at 50 V and up to 120 mA at 250 V. The BF458 transistor must be mounted on a heat radiator and the maximum input voltage is 300 V. The circuit is from a 1978 publication. The adjustment of the output voltage is made in the potentiometer and the FET can be the BF245.
