Patent ID: 6849845

Claim:
An optical sensor for producing an electrical signal in response to electromagnetic radiation, comprising: a photodetector having an output supplying an electrical signal proportional to the intensity of the electromagnetic radiation striking the photodetector; and an integrating circuit coupled with the output of the photodetector to accumulate the electrical signal from the photodetector, said integrating circuit comprising: an operational amplifier having a non-inverting input connected to a non-zero bias voltage, an inverting input coupled to said photodetector, and at least one output; an integrating voltage storage device, having a first terminal coupled to the operational amplifier output, and a second terminal coupled to the operational amplifier inverting input; an output stage comprising a gate terminal, connected to the operational amplifier output, and an output terminal connected to said first terminal of the integrating voltage storage device, and switching circuitry for controlling timing of the integrating circuit and switching the integrating circuit between a reset phase and an integration phase, wherein said switching circuitry includes first switching device for connecting said operational amplifier output to said operational amplifier inverting input during said reset phase, and means for resetting said integrating voltage storage device during said reset phase, a voltage equal to said bias voltage being applied across said integrating voltage storage device, and said first terminal of said integrating voltage storage device being pulled to a reference potential.