This paper proposes an energy-efficient, 12-stage charge pump with constant threshold voltage. This new charge pump utilizes 2 pairs of non-overlapping clocks. Under control of an extra pair of clocks, each charge pump cell (CPC) is equivalent to a switch. Without reduction by a threshold voltage and the limitation of body effects, a higher output voltage than that of the traditional charge pump is obtained by the proposed circuit, which is fabricated in a 0.18 µm complementary metal-oxide semiconductor (CMOS) process. With an input voltage from 0.7 V to 1.4 V, the output voltage range is from 5.8 V to 12.5 V. With a 2-pF load capacitor, the power consumption is only 62.7 µW at maximum DC output voltage of 12.5 V. This circuit is intended to generate an on-chip bias voltage for a microelectromechanical systems (MEMS) microphone.