LOAD DRIVING CIRCUIT AND EXTRACT CIRCUIT FOR THE LOAD DRIVING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To prevent a waveform of an output current from being deteriorated even in the case that a drive current is small in the load driving circuit comprising a differential pair with respect to the load driving circuit that takes a laser and a transmission line as a load. SOLUTION: This circuit is provided with a load differential amplifier drive circuit 1 connecting to a load, a monitor circuit 4 that receives a signal to control a drive current of a current source of the load differential amplifier driving circuit 1 subject to variable control and extracts an input voltage amplitude not causing distortion in a waveform of an output voltage of the load differential amplifier driving circuit 1, and a pre-stage differential circuit 5 that is provided with a differential pair driven by an input signal to provide an output voltage to the load differential amplifier driving circuit 1. An output of the monitor circuit 4 controls the driving current of the pre-stage differential circuit 5.