Patent ID: 6855919

Claim:
A high-frequency current generating circuit for generating a high-frequency currant, incorporated into a driving device for driving a laser diode by using a drive signal for driving one of first and second laser diodes having different wavelengths of emitting light obtained by superimposing said high-frequency current on a control current for controlling an output of said laser diode, said high-frequency current generating circuit comprising: a detection oscillation circuit configured to detect whether the first and second laser diodes are turned on/off while referring to a voltage value generated based on the control current, and output an oscillation signal corresponding to the wavelength of the laser diode being turned on; and two high-frequency current generation units configured to input an output signal of said detection oscillation circuit, and output the high-frequency current, wherein each of said two high-frequency current generation units comprises: an output terminal configured to output the high-frequency current; a first sourcing current source configured to generate a first current, and output the first current to said output terminal; a first current switch configured to control an output of the first current from said first sourcing current source to said output terminal, said first current switch being connected between said first sourcing current source and said output terminal; a second sinking current source configured to generate a second current, and input the second current from said output terminal; a second current switch configured to control an output of the second current from said second sinking current source to said output terminal, said second current switch being connected between said second sinking current source and said output terminal; and a control circuit configured to alternately on/off control said first and second current switches, said control circuit being connected to said first and a first current switch configured to control an output of the first current from said first sourcing current source to said output terminal, said first current switch being connected between said first sourcing current source and said output terminal; a second sinking current source configured to generate a second current, and input the second current from said output terminal; a second current switch configured to control an output of the second current from said second sinking current source to said output terminal, said second current switch being connected between said second sinking current source and said output terminal; and a control circuit configured to alternately on/off control said first and second current switches, said control circuit being connected to said first and second current switches.