A voltage-reducing device of low power dissipation is provided, including a plurality of transistors, which are self-connected as diode equivalent. These transistors are then cascaded in series in the same direction and coupled to a voltage source. Since every transistor has a threshold voltage, the voltage at the end of the forward-biased cascaded transistors will be lowered than the voltage source so as to provide a reduced voltage source. Furthermore, since the voltage adjustment of the device is based on the threshold voltage, there is hardly any power dissipation. In addition, we can use different threshold voltages from various transistors to provide different combinations of these threshold voltages to obtain the desired voltage drop.