A reference voltage generator (100, 400, 700, 800), comprising: a bandgap reference circuit, arranged to generate a reference voltage (VREF) according to at least one base-emitter voltage (VBE') of at least one bipolar junction transistor (Q1, Q2); and a negative voltage generator (104, 200), arranged to generate a negative voltage, wherein at least one base terminal of the at least one bipolar junction transistor (Q1, Q2) of the bandgap reference circuit is arranged to receive the negative voltage as base voltage, wherein the negative voltage generator comprises a charge pump circuit comprising: a first capacitor, having a first end and a second end; a first switch, coupled between a first voltage (V DD) and the first end of the first capacitor; a second switch, coupled between the first end of the first capacitor and a second voltage; a third switch, coupled between the second end of the first capacitor and the second voltage; characterized by: a resistor, having a first end and a second end, wherein the second end is connected to the at least one base terminal of the at least one bipolar junction transistor (Q1, Q2)of the bandgap reference circuit; a fourth switch, coupled between the second end of the first capacitor and the first end of the resistor; and a second capacitor, coupled between the second end of the resistor and the second voltage; wherein the negative voltage is generated at the second end of the resistor; during a first time period, the first switch and the third switch are both switched on, and the second switch and the fourth switch are both switched off; and during a second time period following the first time period, the second switch and the fourth switch are both switched on, and the first switch and the second switch are both switched off. a bandgap reference circuit, arranged to generate a reference voltage (VREF) according to at least one base-emitter voltage (VBE') of at least one bipolar junction transistor (Q1, Q2); and a negative voltage generator (104, 200), arranged to generate a negative voltage, wherein at least one base terminal of the at least one bipolar junction transistor (Q1, Q2) of the bandgap reference circuit is arranged to receive the negative voltage as base voltage, a first capacitor, having a first end and a second end; a first switch, coupled between a first voltage (V DD) and the first end of the first capacitor; a second switch, coupled between the first end of the first capacitor and a second voltage; a third switch, coupled between the second end of the first capacitor and the second voltage; characterized by: a resistor, having a first end and a second end, wherein the second end is connected to the at least one base terminal of the at least one bipolar junction transistor (Q1, Q2)of the bandgap reference circuit; a fourth switch, coupled between the second end of the first capacitor and the first end of the resistor; and a second capacitor, coupled between the second end of the resistor and the second voltage; wherein the negative voltage is generated at the second end of the resistor; during a first time period, the first switch and the third switch are both switched on, and the second switch and the fourth switch are both switched off; and during a second time period following the first time period, the second switch and the fourth switch are both switched on, and the first switch and the second switch are both switched off.