| 摘要 |
<p>PURPOSE:To obtain a circuit able to detect only a pulse light with one operational amplifier by providing three current mirror circuits and adopting a current integration type current mirror circuit integrating a reference current as an output current for one of 2nd and 3rd current mirror circuits. CONSTITUTION:When a photodiode 1 receives a pulse light, an accurate collector current corresponding to a reception pulse light flows to a transistor(TR) Q20. However, since a capacitor C3 connects between a base circuit and ground, a current corresponding to a received pulse light is integrated and a collector current is almost unchanged. As a result, a difference is caused between collector currents I17, I20 of the TRs Q17, Q20 and a difference is caused between voltages caused across resistors R10, R11, resulting in causing an offset voltage. The offset voltage is amplified depending on the ratio of resistors R12, R13 and outputted at an output terminal 4. Thus, only an optical signal changed in terms of AC is selectively amplified among optical signals received by the photodiode 1 and the result is outputted.</p> |
