Patent ID: 8569674

Claim:
A photocurrent monitoring circuit, which performs monitoring by converting photocurrents output from a plurality of photodiodes into voltages and by performing time division multiplexing for the obtained voltages, comprising: a plurality of current mirror circuits respectively connected to each photodiode, for receiving each photocurrent and supplying a photocurrent having the same value as that of the received photocurrent, each current mirror circuit comprising: a first current mirror configured to convert the photocurrent received from the photodiode into an intermediate photocurrent; and a second current mirror configured to convert the intermediate photocurrent into the photocurrent supplied by the current mirror circuit; a multiplexer circuit for selecting one of input terminals to establish a connection of the selected input terminal to an output terminal, wherein the current mirror circuits are respectively connected to the input terminals; and an amplifier for converting a photocurrent which flows from a selected current mirror circuit via the multiplexer circuit into a voltage, and for outputting the voltage, wherein the current mirror circuits are configured to sink current from the photodiodes and source current to the amplifier.