A rapidly regulable high-voltage supply for the electrical focusing of an electron beam using a high-voltage final stage is provided. The high-voltage final stage includes a plurality of amplification elements that are interconnected in a series configuration with a first high-voltage connection, and a potential dividing chain including a series of potential dividing elements. The potential dividing chain is interconnected with the first high-voltage connection and has a signal interconnection with the plurality of amplification elements, so that when a voltage is applied across the potential dividing chain, a difference in voltages between a signal input to any amplification element of the plurality of amplification elements and a signal input to a next amplification element of the plurality of amplification elements has a same sign.