Display-integrated type tablet device

摘要

A detection and hold circuit (24) outputs a reference signal having a level proportional to an x-coordinate detection pulse input from an X-coordinate signal amplifier (23). A delay element (25) delays the reference signal. An adder (26) adds the x-coordinate detection pulse from the X-coordinate signal amplifier (23) and a delayed signal from the delay element (25). Comparators (27) and (30) obtain a coordinate detection pulse making a detection signal from another detection and hold circuit (33) for an LCD voltage inversion pulse serve as a reference signal. Thus noise following the x-coordinate detection pulse is removed to generate a coordinate detection pulse with a reference value corresponding to the level of the LCD voltage inversion pulse to allow a stable coordinate detection to be achieved. A correction signal generation circuit (4) reads out correction data stored in an internal memory and transmits the data as a correction signal to a correction voltage generation circuit (5) in an x-coordinate detection period when the segment electrode (X) placed in the lower position is scanned. The correction voltage generation circuit (5) generates a correction voltage (V1') for canceling a voltage induced at the common electrode (Y) placed in the upper position based on the input correction signal and a bias power source (V1) input from a DC power supply circuit (6).