| 摘要 |
PROBLEM TO BE SOLVED: To improve an optical reception characteristic.SOLUTION: A differential optical front end 120 includes TIAs 121, 122 and a differential amplification circuit 123. The TIAs 121, 122 are a non-feedback TIA whose output is not fed back to an input. The TIA 121 converts a current signal output from a photodiode 110 to a voltage signal. The TIA 121 outputs the voltage signal to a non-inverting input terminal of the differential amplification circuit 123. The TIA 122 outputs a voltage signal to an inverting input terminal of the differential amplification circuit 123. The differential amplification circuit 123 differentially amplifies the voltage signals output from the TIAs 121, 122. On the basis of a normal phase signal and a reverse phase signal output from the differential amplification circuit 123, an offset compensation function of an offset compensation amplifier 150 and an offset compensation resistor 160 inputs into the TIA 122 an offset current signal depending on an offset between the level of the normal phase signal and the level of the reverse phase signal. |
