Capacitive touch sensing circuit

A capacitive touch sensing circuit, comprising:

• an operational amplifier having a first input terminal, a second input terminal and an output terminal, the second input terminal receiving a reference voltage;
• a parallel capacitor, coupled between the first input terminal of the operational amplifier and the output terminal;
• a series capacitor, coupled between the first input terminal of the operational amplifier and a first node;
• a sensing capacitor, coupled between the first node and a ground terminal;
• a test capacitor, coupled between a second node and the ground terminal;
• a first switch, coupled between an operating voltage and the first node;
• a second switch, coupled between the first node and the ground terminal;
• a third switch, coupled between the ground terminal and the second node;
• a fourth switch, coupled between the operating voltage and the second node;
• a first current source, coupled to the operating voltage;
• a second current source, coupled to the ground terminal;
• a fifth switch, coupled between the first current source and the first node;
• a sixth switch, coupled between the first node and the second current source;
• a seventh switch, coupled between the second node and a third node, wherein the third node is disposed between the series capacitor and the first input terminal of the operational amplifier;
• and
• an eighth switch, coupled in parallel with the parallel capacitor and coupled between the first input terminal of the operational amplifier and the output terminal.