Preamplifier for high speed optical fiber communication system

摘要

A trans-impedance type preamplifier for an optical communication system with a high conversion gain and a wide band is provided, in which a preamplifier suppresses obvious peaking and has a flat gain characteristic over a high frequency range and a wide dynamic range. In the trans-impedance type preamplifier, the preamplifier includes an amplifier circuit, a feedback circuit, and a control circuit. The amplifier circuit includes a source grounded input FET for amplifing an electrical signal and a cascade-connected FET to which resistances are connected. Further, FET to which an output signal from the drain of the cascade-connected FET is input, a level shift diode, and an electrical current source FET are included therein. An output terminal is connected to the drain of the electrical current source FET. The feedback circuit has a circuit portion in which the first feedback resistance is connected to input and output terminals of the amplifier circuit and a feedback FET connected to the first feedback resistance in parallel and the second feedback resistance are connected to the feedback FET in series. Further, a capacitor connected to the second feedback resistance in parallel is included therein. An output signal from the control circuit is input to the gate of the feedback FET of the feedback circuit.