| 摘要 |
PURPOSE:To attain high voltage control with less current capacity by means of simple circuit constitution by using an AGC voltage so as to control the amplitude of an output pulse of a pulse generating circuit, and obtaining a DC high voltage applied to an APD element from the controlled pulse signal by a multiplication voltage rectifier circuit. CONSTITUTION:Pulse signals whose phases differ by 180 deg. from a pulse oscillating circuit 1 are supplied to an amplitude variable circuit 2. On the other hand, an optical signal is converted into an electric signal by an APD element 3 being a photodetector and amplified by an amplifier 4 and outputted as an output signal. A voltage multiple amplification rectifier circuit 11 receiving each pulse signal from the amplitude variable circuit 2 generates a DC high voltage for being applied to the APD element 3, thereby controlling the multiple factor of the APD element 3. Since the amplitude of the pulse signal with a low level is controlled while not employing voltage control using a high DC voltage to a load, the current capacity with a high voltage for the APD element is obtained sufficiently even with a capacitance of 0.01muF or below of the capacitor for the circuit 11.
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