| 摘要 |
PURPOSE:To remove high-frequency noise wave, by selecting a higher responding frequency during a non-sampling period with synchronization with sampling of an optical signal and a lower responding frequency during a sampling period. CONSTITUTION:A time-constant circuit RC is inserted between a preamp A1 and a buffer amplifier A2 and either one of resistances R1, R2 is selected by a selecting switch SS. A resistance value of the resistance R1 is higher than that of R2 and consequently, the responding frequency of a measuring circuit up to the amplifier A2 becomes low for the resistance R1 and high for the resistance R2. A sampling pulse from a controlling circuit K is transmitted to the selecting switch SS via a NOR circuit NOR. When the sampling pulse is zero, the output of the NOR circuit is on the H-level and the resistance R2 is selected with a higher responding frequency of the measuring circuit and when the sampling pulse is existing, the output of the circuit NOR is on the L-level and the resistance R1 is selected with low responding frequency and high-frequency noise is removed during the sampling operation period.
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