Amplifying circuit and optical receiver comprising the same

Abstract

A first differential amplifier amplifies an input signal and differential-outputs an amplified result in the form of a positive-phase output and a negative-phase output. First and second peak detecting parts respectively detect and store peak values of the positive-phase and negative-phase outputs of the first differential amplifier. A second differential amplifier amplifies a difference between outputs of the first and second peak detecting parts and then differential-outputs an amplified result in the form of a positive-phase output and a negative phase output. The positive-phase and negative-phase outputs of the second differential amplifier coincide with center values of the positive-phase and negative-phase outputs of the first differential amplifier, respectively. A combined differential amplifier amplifies a difference {(V,−V,)−(V,−V,)} between a difference (V,−V,) of a first input signal (V,) and a fit reference signal (V,) and a difference (V,−V,) of a second input signal (V,) and a second reference signal (V,). The first and second input signals are assigned to the positive-phase and negative-phase outputs of the first differential amplifier, respectively. The first and second reference signals arc assigned to the positive-phase and negative-phase outputs of the second differential amplifier, respectively. Preferably, an output value of the first differential amplifier receiving no signal input and an output value of the second differential amplifier receiving no signal input are set to be equal.