Directly modulated laser drive circuit

A directly modulated laser driving circuit comprising:

• a power supply circuit configured to supply a driving current to a laser diode;
• and
• a driver circuit connected in parallel to the laser diode, configured to bypass the driving current in accordance with an input modulating signal,
• wherein the driver circuit comprises a plurality of cascode-connected NMOS transistors,
• the modulating signal is applied to a gate terminal of a lowermost stage transistor located at a lowermost stage out of the NMOS transistors, and
• an upper stage bias potential that is a sum of a minimum gate-source voltage and a maximum drain-source voltage of a transistor located immediately below an upper stage transistor located at an upper stage above the lowermost stage transistor of the NMOS transistors is applied to a gate terminal of the upper stage transistor.