Patent ID: 7522487
Filing Date: 2009-04-21
Classification: H03F

Abstract:
1. A light receiving amplifier circuit comprising: a light receiving element which converts received light into a current and outputs the current thus converted; a current-to-voltage conversion circuit which converts the output current of the light receiving element into a voltage; a reference voltage supplying amplifier having an identical structure with the current-to-voltage conversion circuit except that the light receiving element is not connected and a band limiting capacitor is provided; and a differential amplifier circuit which amplifies a difference between the output voltage of the current-to-voltage conversion circuit and a reference voltage that is an output voltage of the reference voltage supplying amplifier, the current-to-voltage conversion circuit and the reference voltage supplying amplifier each including: a grounded-emitter amplifier circuit employing a grounded-emitter transistor, the grounded-emitter transistor having a base serving as an input terminal, and a terminal serving as an output terminal for obtaining an output voltage which varies depending on an output from an output node of the grounded-emitter amplifier circuit; and a plurality of feedback resistors being provided in parallel on feedback paths from the output terminal to the base so as to be selectively used, the band limiting capacitor being connected between the output node of the grounded-emitter amplifier circuit and a grounded point where the emitter is grounded.