| 摘要 |
<p>PURPOSE:To improve coordinate detection accuracy by adding a capacity eliminating circuit to an electrostatic capacity system touch detecting device, and reducing stray capacity. CONSTITUTION:A capacity eliminating circuit 36 is connected to a capacity terminal of a capacity variable digital oscillator 29 being a capacity measuring circuit. In such a case, the stray capacity is formed mainly by an input/output capacity of an analog switch 27, and it is about 500pF. As for the capacity eliminating circuit 36, a non-inversion amplifier 37 of an amplification factor mu=2 is used, the potential of the capacity terminal of the oscillator 29 is inputted, and the capacity of C=400pF is connected to its output end. This circuit goes to a negative capacity of -400pF equivalently. As a result, the equivalent capacity which is seen from the oscillator 29 goes to 500-400pF=100pF, and the stray capacity is reduced. In such a way, the coordinate detection accuracy can be improved.</p> |
