| 摘要 |
PURPOSE:To make amplification possible in which in-phase noise superposed to a signal is canceled, by providing the positive side and the negative side of a power source for a photoelectric conversion element with the same impedance elements, and extracting the respective signals from both terminals of the photoelectric conversion element. CONSTITUTION:An impedance element 3, a photo diode 1, and an impedance element 4 are connected in series from the positive pole E of a power source to a negative pole of the power source. When the photo diode 1 is irradiated by light, a current i1 flows through an impedance element 4. Taking the value of the impedance element 3 and that of the impedance element 4 as z1 and z2, respectively, a voltage v1=i1Xz1 and a voltage v2=i2Xz2 generate at the terminal B of the photo diode 1 and the terminal C of the photo diode 1, respectively. In the case of z1=z2, it follows that v1=v2. As the phase of a signal generating at the terminal B is inverse to that of a signal generating at the terminal C, the terminals B and C are connected to a differential amplifier. Thereby, the signals are added with each other and amplified, so that the in- phase noise is cancelled.
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