Equalizing and amplifying circuit in an optical signal receiving apparatus.

摘要

Disclosed is an equalizing and amplifying circuit in an optical signal receiving apparatus comprising a preamplifier circuit (102a) having an input terminal (406) connected to the output of a light receiving element (101), the preamplifier circuit amplifying the electrical signal from the light receiving element to output an amplified signal, and comprising an automatic gain control circuit (103) connected to the output of said preamplifier circuit. The preamplifier circuit (102a) comprises a transistor (402) having a common-base, a current source (403) connected to the emitter of the transistor, for supplying a bias current to the transistor, and a load resistor (404) connected to the collector of the transistor. The emitter of the transistor is connected to the input terminal (406), and the collector of the transistor is connected to the output terminal (409). Whereby, a negative influence caused by mounting the circuit on a package can be avoided and the circuit can operate stably in a high frequency range.