| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal amplifier circuit that is used for e.g. a reception section of an optical communication system and prevents a signal amplified by the amplifier circuit at recovery of a pulse signal from being limited and compensates an offset of each circuit so as to suppress fluctuations in a pulse width of an output signal. SOLUTION: The signal amplifier circuit is provided with an automatic threshold value setting section 2 that has a peak detection circuit holding a peak level of an input signal and a bottom detection circuit holding a bottom level of the input signal to select prescribed voltage divisions of the peak level and the bottom level for threshold values, an automatic gain control amplifier section 3 that receives the input signal and the threshold values from the automatic threshold value setting section 2 to differentially amplify them, and a gain control section 4 that detects level information from a difference between the peak level and the bottom level and supplies a gain control signal corresponding to the level of the input signal to the automatic gain control amplifier section 3 as a feedforward signal.
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