A drive circuit that generates a driving signal for driving an optical modulator by amplifying a differential input signal including a positive-phase component having a phase and a negative-phase component having a phase opposite to the phase of the positive-phase component, the drive circuit comprising:
- an input terminal configured to receive the differential input signal;
- a first emitter follower circuit configured to receive the differential input signal via the input terminal, lower a voltage of the differential input signal by a first voltage value, and output a lowered differential input signal as a first differential signal including a positive-phase component having a phase and a negative-phase component having a phase opposite to the phase of the positive-phase component of the first differential signal;
- a level shift circuit configured to lower a voltage of the first differential signal by a second voltage value and output a lowered first differential signal as a second differential signal including a positive-phase component having a phase and a negative-phase component having a phase opposite to the phase of the positive-phase component of the second differential signal;
- a first differential circuit including a pair of first transistors each having a base, an emitter, and a collector and a first current source electrically connected in common with the emitters of the first transistors, and configured to receive the negative-phase component of the first differential signal at the base of one of the first transistors, receive the positive-phase component of the first differential signal at the base of another of the first transistors, output a positive-phase component of a third differential signal that includes the positive-phase component having a phase and a negative-phase component having a phase opposite to the phase of the positive-phase component of the third differential signal from the collector of the one of the first transistors, and output the negative-phase component of the third differential signal from the collector of the another of the first transistors;
- a second emitter follower circuit including a pair of second transistors each having a base, an emitter, and a collector, and configured to receive the positive-phase component of the third differential signal at the base of one of the second transistors and receive the negative-phase component of the third differential signal at the base of another of the second transistors;
- a second differential circuit including a pair of third transistors each having a base, an emitter, and a collector and a second current source electrically connected in common with the emitters of the third transistors, and configured to receive the negative-phase component of the second differential signal at the base of one of the third transistors and receive the positive-phase component of the second differential signal at the base of another of the third transistors;
- and
- an output terminal electrically connected to one of a first output node electrically connected to the emitter of the one of the second transistors and the collector of the one of the third transistors and a second output node electrically connected to the emitter of the another of the second transistors and the collector of the another of the third transistors, and configured to output the driving signal.