| 摘要 |
PURPOSE:To detect minute electric charge of nearly 0.1pc by providing a capacitor having an impedance equal to that of a charge detection element and an analog multiplexer to select the capacitor and providing an analog switch between the analog multiplexer and an integration circuit so as to cancel feed- through. CONSTITUTION:Dummy capacitors CB0-CB63 corresponding to photodiodes DA0-DA63 are provided and analog switches SB0-SB63 corresponding to analog switches SA0-SA63 are provided to constitute fully differential constitution for the entire circuit. Thus, the feed-through of the analog switches comprising the in-phase component is cancelled and only a voltage corresponding to an electric charge generated in the photodiodes DA0-DA63 appears at an output Vo. |
