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A light detecting circuit in which noise superposed on a bias voltage of a photodiode is substantially canceled without the aid of a filter circuit employing an inductor. The photodiode is connected between a bias voltage terminal and an inverting terminal of a main amplifier, the latter being imple

A light detecting circuit in which noise superposed on a bias voltage of a photodiode is substantially canceled without the aid of a filter circuit employing an inductor. The photodiode is connected between a bias voltage terminal and an inverting terminal of a main amplifier, the latter being implemented with a differential amplifier or a comparator. A capacitance device is connected between the same bias voltage terminal and the other (noninverting) input terminal of the main amplifier. The capacitance device may be either a physical capacitor or a second photodiode which, in either case, should have a capacitance equal to the parasitic capacitance of the first photodiode.

대표청구항 ▼

A light detecting circuit comprising: a first photodiode receiving an optical signal and converting said optical signal into an electrical signal, said first photodiode being coupled to a bias voltage source; a main amplifier receiving said electrical signal upon one of two input terminals thereof f

A light detecting circuit comprising: a first photodiode receiving an optical signal and converting said optical signal into an electrical signal, said first photodiode being coupled to a bias voltage source; a main amplifier receiving said electrical signal upon one of two input terminals thereof for amplifying said electrical signal; and capacitance means connected to the other input terminal of said main amplifier and to said bias voltage source for canceling noise mixed in said circuit through a parasitic capacitance of said first photodiode from said bias voltage source.