| 摘要 |
<p>In an image sensor, a photo detector circuit (305) provides a detection quantity (308) having a level that depends on an amount of light to which the photo detector circuit has been exposed during a photo detection time interval. A front-end circuit (306) provides an output signal (309) indicative of the amount of light in response to at least one input signal, among which is the detection quantity (308). The front-end circuit comprises a transistor (315) having a threshold voltage that affects a relationship between the output signal (309) and the level of the detection quantity (308). This transistor (315) has a biasing node (319) via which a biasing voltage (320) can be applied to a semiconductor region (318) that affects the threshold voltage of the transistor. A replica (1401) of the front-end circuit receives at least one defined input signal (1406, 1407), among which is a substitute of the detection quantity (308) having a defined level (1406). The replica (1401) is arranged in a control loop (1408) that controls the biasing voltage (320) that is applied to the biasing node in the replica, so that the replica (1401) provides a defined output signal (1412). This biasing voltage (320) is then also applied to the biasing node (319) in the front-end circuit.</p> |
