To prevent the occurrence of condition in which the bias voltage is out of an allowable voltage range for a long interval by conducting recharging control and discharging control of a bias voltage using a single comparator.

A voltage supplying circuit is provided with a recharging and discharging section 7 which recharges and discharges a bias voltage, a reference voltage generating section 1 which generates an upper limit reference voltage, a central reference voltage and a lower limit reference voltage from a power supply voltage for the bias voltage, a selection section 2 which selects any one of the reference voltages, a comparison section 3 which compares the selected reference voltage with the bias voltage, a mode setting section 4 which sets either the recharging mode or the discharging mode in accordance with the comparison result of the bias voltage and the central reference voltage during a timing signal setting, a selection control section 6 which outputs a selection control signal to the section 2 and a recharging and discharging control section 5 which outputs recharging discharging control signal to the section 7 in accordance with the comparison result of the section 3.