US Patent 10289221 Electrostatic pen

An electrostatic pen has a switch, control circuitry to control the switch and a pen point electrode. The switch has first, second and third terminals and a first diode having an anode coupled to the first terminal and a cathode coupled to the third terminal. The pen point electrode is coupled to the first terminal of the switch. The control circuitry, in operation, supplies respective potentials to the second terminal and the third terminal of the switch and switches between two or more states including a first state in which a potential of the second terminal is higher than a potential of the third terminal and a second state in which the potential of the second terminal is equal to or lower than the potential of the third terminal.