Filtering circuit and touch display device

A touch display device, comprising:

• a substrate;
• pixel electrodes arranged on the substrate;
• at least one common electrode arranged on the substrate to load a common voltage in a display phase and to load a touch signal in a touch phase;
• a signal source configured to provide a display signal or the touch signal, wherein the display signal includes the common voltage;
• wherein the common voltage is a direct current signal, and the touch signal is an alternating current signal;
• at least one common electrode lead electrically connected to the signal source directly and the common electrode to input either the common voltage or the touch signal to the common electrode;
• at least one filter capacitor comprising a first terminal and a second terminal, wherein a fixed electric voltage is applied to the second terminal of the filter capacitor;
• and
• at least one control switch arranged between the common electrode lead and the first terminal of the filter capacitor to electrically connect the filter capacitor with the common electrode lead or electrically disconnect the filter capacitor from the common electrode lead;
• wherein the control switch comprises a transistor, including a gate electrode, a first electrode and a second electrode, the gate electrode of the transistor receives a control signal as an input, wherein the first electrode of the transistor is electrically connected to the common electrode lead, and the second electrode of the transistor is electrically connected to the first terminal of the filter capacitor;
• wherein:
• the transistor is switched on in the display phase, so that the first terminal of the filter capacitor connects electrically to the signal source;
• and
• the transistor is switched off in the touch phase, so that the first terminal of the filter capacitor electrically disconnects from the signal source.