Controllable high voltage source having fast settling time

A high voltage dc stepping power supply for sampling a utilization device such as an electrostatic analyzer has a relatively fast settling time for voltage steps. The supply includes a waveform generator for deriving a low voltage staircase waveform that feeds a relatively long response time power supply, deriving a high output voltage generally equal to a predetermined multiple of the input voltage. In the power supply, an ac voltage modulated by the staircase waveform is applied to a step-up transformer and then to a voltage multiplier stack to form a high voltage, relatively poor replica of the input waveform at an intermediate output terminal. A constant dc source, applied to the input of the power supply, biases the voltage at the intermediate output terminal to be in excess of the predetermined multiple of the input voltage.