Patent ID: 7763838
Filing Date: 2010-07-27
Classification: G01J,H03F

Abstract:
1. A photodetecting circuit comprising: an adder, selectively adding outputs of a plurality of circuits for photodetection; each of the circuits for photodetection in turn comprising: a photodetecting element; a transimpedance amplifier for photodetection, with a first input terminal connected to the photodetecting element; a transconductance amplifier, with a first input terminal connected to an output terminal of the transimpedance amplifier for photodetection; and a feedback circuit, connected between the output terminal of the transimpedance amplifier for photodetection and the first input terminal of the transimpedance amplifier for photodetection and applying feedback to keep fixed an output voltage of the transimpedance amplifier for photodetection; wherein the feedback circuit comprises: a error amplifier for feedback, with a first input terminal connected to the output terminal of the transimpedance amplifier for photodetection and a reference voltage for photodetection being input into a second input terminal; a smoothing circuit, with an input terminal connected to an output terminal of the error amplifier for feedback; and a feedback transistor, with a control terminal connected to an output terminal of the smoothing circuit and a terminal, connected to the photodetecting element, being connected to the first input terminal of the transimpedance amplifier for photodetection.