LIGHT EMITTING ELEMENT DRIVE CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a light emitting element drive circuit improving the deterioration in a bit error rate in the communication system by controlling a mark rate of a binary signal driving the light emitting element to be a known mark rate so as to prevent waveform deterioration in the optical signal of the light emitting element caused by a fluctuation in a bias component of the binary input signal and a threshold level. SOLUTION: A binary input signal (A) whose waveform is unsharpened is compared with a threshold level (D) by a comparator circuit 2 and becomes a shaped binary signal and it is used to drive a light emitting element 6 via a load drive circuit 1. A mark rate detection circuit 3 detects a mark rate (C) of a shaped binary signal (B) to give it to a threshold level control circuit 4. The threshold level control circuit 4 controls the threshold level (D) so that the shaped binary signal (B) has a known mark rate of the binary input signal (A). Thus, waveform deterioration in the optical output of the light emitting element 6 caused by the fluctuation in the bias component of the binary input signal (A) and the threshold level (D) is prevented and the deterioration in the bit error rate of the communication system is improved in the light emitting element drive circuit.