Photosensor device with dark current cancellation

摘要

A photosensor device with dark current cancellation is disclosed. The photosensor device comprises a first and second photosensors, a first and second current replication circuits and a digital signal generator. The first photosensor has a first dark current but does not receive any photo signal. The second photosensor has a second dark current and receives a photo signal to generate photocurrent according to the photo signal. The first current replication circuit generates a replicated current according to the first dark current and injects the replicated current into the second photosensor for cancelling the second dark current from the second photosensor. The second photosensor is coupled to the second current replication circuit which generates charge and discharge currents according to the photocurrent of the second photosensor. The second current replication circuit is coupled to a digital signal generator which generates digital signals according to the charge and discharge functions, and the electrical characteristic of the digital signal is related to the intensity of the photo signal.