| 摘要 |
In an infrared data-receiving circuit wherein an output electric current of a photodiode is current-to-voltage converted by a preamplifier and, after having been amplified by an amplification circuit, is subjected to a waveform-shaping operation in a comparator by using a predetermined threshold value, the threshold voltage, upon receipt of a low signal voltage, is set at the average value Vav that has been formed by two LPFs and, upon receipt of a high signal voltage, is also set at a shift value that has been obtained by allowing the voltage, which has been generated by shifting of a level shift circuit, to be sampled by a peak-hold circuit constituted of a differential amplifier. Thus, the apparatus is allowed to deal with a wide dynamic range. Moreover, in this arrangement, a single capacitor may be commonly used for an integrating operation in the LPFs and for a holding operation in the peak-hold circuit so as to provide a simple construction that is preferably applied to an integrated circuit. Consequently, in the infrared data-receiving circuit that uses the output from the photodiode by subjecting it to the waveform-shaping operation, it becomes possible to deal with a wide range of level differences by using a simple construction.
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