Patent ID: 7620332
Filing Date: 2009-11-17
Classification: H03F,H04B

Abstract:
1. An optical receiving unit for outputting an electrical output signal by receiving an optical signal, the optical receiving unit comprising: an O/E-converter for receiving said optical signal and outputting an electrical signal corresponding to said optical signal, the O/E-converter including a light-receiving device to receive the optical signal and to output a photocurrent, and including a trans-impedance amplifier to convert the photocurrent into the electrical signal; a signal processing unit having an input coupled in an AC mode with the O/E-converter through a capacitor for receiving said electrical signal and an output for outputting said electrical output signal, wherein the input of the signal processing unit includes a differential circuit with a first input terminal and a second input terminal for receiving complementary electrical signals corresponding to the optical signal; and an offset voltage setting unit to apply a respective offset voltage to each of the first and second input terminals of the signal processing unit to compensate for temperature dependence of the signal processing unit, the offset voltage setting unit including a first amplifier, a second amplifier and a bias source, wherein the first and second amplifiers are connected in series with each other, the first amplifier includes a differential circuit with two inputs coupled to respective inputs of the offset voltage setting unit, an output of the second amplifier is connected to one of two inputs of the first amplifier, the first amplifier is arranged to operate as a low pass filter, and the bias source is coupled to an input of the second amplifier and arranged to output a bias voltage depending on an operating temperature of the optical receiving unit.