A charge pump is provided in the same integrated circuit chip as a control means which permits selectively connecting any of one or more electrodes with conductors along a lead. The charge pump derives about two volts from a one-volt supply, and becomes stable within a few tens of microseconds. The charge pump may be composed of three doublers—the first generating timing signals for the second and third doublers, with the second and third doublers working out of phase with each other.
