The invention provides sodium channel modulating compounds which are useful for treating diseases or conditions associated with sodium channel activity, such as neuropathic pain. The unit can be set to throw the balls in the air or on the ground so a variety of situations can be practiced. The high-voltage output transistor protects the low voltage devices of the multi-stage charge pump, by preventing the controlled output voltage from undergoing excessively abrupt variations, that could damage the transistors of the last stage of the charge pump.