Patent ID: 8134106

Claim:
A current detection circuit for detecting current flowing in a light receiving device connected to a detection terminal, the current detection circuit comprising: a first transistor, one end thereof connected to a first end of a main current path including the light receiving device and the detection terminal, a potential of a second end of the main current path being fixed; a bias current path which is on-off controllable, a first end thereof connected to the first end of the main current path, a second end thereof connected to the second end of the main current path; and a second transistor which configures a current mirror circuit with the first transistor and forms output of the current detection circuit by multiplying the current flowing in the first transistor by a predetermined factor, wherein the bias current path is configured to turn on prior to the start of light reception of the light receiving device, and a sum of the current through the main current path and the current through the bias current path flows into the first transistor.