| 摘要 |
PROBLEM TO BE SOLVED: To provide a DC offset cancel circuit capable of canceling a DC offset voltage, which is generated in the differential output signal of a differential amplifier circuit, while preventing the distortion of a signal waveform caused by the storage of AC components and an optic/electric pulse converting circuit capable of generating an electric pulse signal, with which rise or fall time of an optical pulse signal is accurately reproduced, by canceling the DC offset voltage. SOLUTION: An optic/electric pulse converting circuit 100 is provided with a photodiode PD, an I/V converting circuit IV, a first differential amplifier circuit AMP1 having a DC offset cancel circuit 110, a second differential amplifier circuit AMP2, a reference voltage generating circuit REFG and a comparator circuit CMP. In the DC offset cancel circuit 110, the state of a low-pass filter LPH with hold function is switched by a switching circuit SW synchronously with an inverted electric pulse signal xRX and a filtered signal, with which the low frequency of third differential signals V3P and V3M is passed and filtered, or hold filtered signal, with which a filtered signal in switching is held, is negatively fed back. |
