A circuit buffer for outputting a voltage signal having a magnitude greater than a withstand voltage of any circuit element in the circuit buffer includes a first transistor and a second transistor. The first transistor includes a first terminal and a second terminal electrically connected to an input terminal and an output terminal of the circuit buffer respectively, a third terminal electrically connected to a first power supply terminal, and a fourth terminal electrically connected to the third terminal of the first transistor. The second transistor includes a first terminal and a second terminal electrically connected to the input terminal and the output terminal of the circuit buffer respectively, a third terminal electrically connected to a second power supply terminal, and a fourth terminal electrically connected to the third terminal of the second transistor. Voltages of the first and second power supply terminal are switched between two different levels, respectively.