Patent ID: 8878812

Claim:
A signal processing device comprising: a touch panel comprising, a plurality of pairs of touch pads, each of the touch pads being a first kind of touch pad, a second kind of touch pad, a third kind of touch pad or a fourth kind of touch pad, and each of the pairs of touch pads comprising two touch pads of a same kind or two touch pads of two different kinds, wherein each of the touch pads of the same kind are commonly connected to respective one of a first, second, third, or fourth output, each pair of touch pads arranged on a substrate and neighboring at least one other pair of touch pads and touch pads of different kinds are not commonly connected; an excitation pad disposed between neighboring two of the pairs of touch pads; and a signal processing circuit for the touch panel comprising, an alternating current power supply providing the excitation pad with an alternating voltage, an electric charge amplifier generating a first output voltage corresponding to a difference between a capacitance of a first capacitor formed between the excitation pad and the first kind of touch pad and a capacitance of a second capacitor formed between the excitation pad and the second kind of touch pad and generating a second output voltage corresponding to a difference between a capacitance of a third capacitor formed between the excitation pad and the third kind of touch pad and a capacitance of a fourth capacitor formed between the excitation pad and the fourth kind of touch pad; and a delta sigma type ND converter converting each of the first and second output voltages generated by the electric charge amplifier into a digital value.