Patent ID: 7856039

Claim:
A semiconductor device for driving a semiconductor laser using a drive current combining a bias current and a switching current by controlling the drive current to obtain a predetermined amount of light to be emitted by the semiconductor laser, the semiconductor device comprising: a switching current control terminal for controlling the switching current; a switching current setting terminal for setting a value of the switching current; a switching current generator circuit configured to generate and output the switching current such that a voltage input to the switching current setting terminal is equal to a voltage input to the switching current control terminal; a bias current control terminal for controlling the bias current; a bias current setting terminal for setting a value of the bias current; a bias current generator circuit configured to generate and output the bias current so that a voltage input to the bias current setting terminal is equal to a voltage input to the bias current control terminal; a memory circuit configured to receive a voltage according to an amount of light emitted by the semiconductor laser and generate a voltage to make the input voltage equal to a predetermined first reference voltage that corresponds to a predetermined amount of light, store the generated voltage, and output the stored voltage; an APC output terminal for outputting the voltage output by the memory circuit to an external device; and a current adding circuit configured to combine the switching current and the bias current to generate the drive current to drive the semiconductor laser.