Patent ID: 7557590

Claim:
A capacitance detection circuit, comprising: a first buffer amplifier, wherein an input of said first buffer amplifier is connected to a capacitor to be detected by a signal wire; a first diode and a second diode, connected in series, the anode of the first diode connected to the cathode of the second diode at a first junction point, and the anode of the second diode connected to the signal wire, and the cathode of the first diode connected to a first power supply; a third diode and a fourth diode, connected in series, the anode of the third diode connected to the cathode of the fourth diode at a second junction point, and the cathode of the third diode connected to the signal wire, and the anode of the fourth diode connected to a second power supply; wherein: an output terminal of the first buffer amplifier is connected to the first junction point of the first diode and the second diode via a first capacitance; said output terminal of the first buffer amplifier is connected to the second junction point of the third diode and the fourth diode via a second capacitance; the first junction point is connected to a point having a voltage whose value is between the voltage of the first power supply, and the voltage of the signal wire, via a first resistor; the second junction point is connected to a point having a voltage whose value is between the voltage of the second power supply and the voltage of the signal wire, via a second resistor.