A voltage generating system including: a voltage source, a clock generating circuit, and a voltage generating circuit. The voltage source generates a reference voltage. The clock generating circuit generates a first clock signal and a second clock signal according to the reference voltage. The voltage generating circuit including an output circuit and a switch circuit. The output circuit generates a control signal at a control node according to the first clock signal and the reference voltage, generates an output signal at an output node according to the second clock signal and the reference voltage. An absolute value of an amplitude of the output signal is greater than the reference voltage while an absolute value of an amplitude of the control signal is greater than the reference voltage. The switch circuit selectively outputs the output signal to an output terminal according to the control signal.