A charge pump for negative voltages, having at least one stage including a high-voltage terminal and a low-voltage terminal; a first branch and a second branch, which are symmetrical and are connected between the high-voltage terminal and the low-voltage terminal and each of which comprises a respective...http://www.google.com.au/patents/US6819162?utm_source=gb-gplus-sharePatent US6819162 - Charge pump for negative voltages
