| 摘要 |
An optical receiver of wide-dynamic range characteristic that stably reproduces a burst signal having different light receiving levels. A preamplifier converts an output from a light receiving element into a voltage signal. A level detecting circuit includes: a first level detecting unit having a shorter time constant; and a second level detecting unit having a longer time constant and switching over to any of the level detecting units in response to a time constant switching signal to detect a voltage level of an output voltage signal output from the preamplifier. An amplifier variably controls conversion gain of the preamplifier based on the detecting result. A time constant switching control outputs the time constant switching signal to the level detecting unit based on the output voltage signal from the preamplifier, to select the first level detecting unit or the second detecting unit based on a number of consecutive identical digits being equal to, smaller, or larger than the predetermined number.
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