Patent ID: 7635837
Filing Date: 2009-12-22
Classification: H03F

Abstract:
1. An optical receiving circuit comprising: a first transimpedance amplifier configured to convert an input signal to a voltage signal, the input signal being current-converted by a first photodiode; a second transimpedance amplifier connected to a light-shielded second photodiode, and being configured to output a reference voltage; a differential amplifier having a first terminal and a second terminal, and being configured to amplify a difference between the voltage signal inputted to the first terminal and a signal inputted to the second terminal; a transconductance amplifier configured to receive as input a branch of the voltage signal and output a current signal to the second terminal; a voltage source configured to superimpose an offset voltage on the output voltage of the second transimpedance amplifier; and a conversion element provided between the voltage source and the second terminal, and being configured to voltage-convert the current signal, wherein, when the voltage signal begins to rise, the transconductance amplifier begins to start up and the signal inputted to the second terminal varies to follow the voltage signal.