| 摘要 |
PURPOSE:To reduce dark current to substantially zero by a method wherein a photo receiving diode and a compensation diode which has the area of 1/m and a photo receiving surface covered with a metal deposited film are provided on the same chip, the output of the compensation element is multiplied by m-times, and the difference is arithmetically amplified. CONSTITUTION:The photo receiving diode 1 of the area S and the compensation diode 2 of S/m are provided on the same chip, the output of each is amplified in pre-amplifiers 3 and 4 at an equal rate, and then the output of the amplifier 4 is amplified 5 further to (m) times and inputted to an operational amplifier 6 together with the output of the amplifier 3. The compensation diode 2 shields light by being covered with an Al7 after being covered with a SiO2. Since the temperature characteristic of dark current does not vary with areas, if the ratio of the dark current is (m) at a temperature, the components of dark current in the output V+ of the amplifier 3 and the output V- of the amplifier 5 are equal even in the change of temperature; accordingly the outputs of the element 2 are all dark currents. Therefore, when the value of V+-V- is arithmetically amplified 6, the component of dark current can be completely removed from the output V+, and then an effective photo receiving circuit can be obtained. |
