| 摘要 |
PURPOSE:To obtain a titled driving device operated with high accuracy by providing an analog switch made nonconductive at all times to the driving device using plural analog switches to cancel mutual leakage currents. CONSTITUTION:A signal from a photoelectric converting circuit 13 is inputted to an operational amplifier 12 when an analog switch 1 is turned on and other switches 3, 5 are turned off, a potential rise of a point Q due to the leakage current of the switches 3, 5 turned off is nearly 10mV and it is superimposed on the signal component. When the signal exceeds the threshold value and the signal level is discriminated in error. In this case, a leakage current compensating switch 35 of the same constitution as switches 1-6 is provided and the capacitance of a capacitor 40 is set to 1/(N-1) [N is the number of analog switches] to the parasitic capacitance, then the rising component of points Q, T due to the leakage current is identical and cancelled together, and only the signal component is outputted to a terminal 11. |
