| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic gain controller, having a small fluctuation in the amplitude of an output signal, even if a leakage current is generated from an ESD protective circuit in an IC chip. SOLUTION: The automatic gain controller comprises a variable gain amplifier 1, an amplitude detector 2 and a gain control circuit 3, and the variable gain amplifier 1 has an operational amplifier 11, a reference voltage source 12, a variable resistance means 13, a resistor 14, an input terminal 44 and an output terminal 51. The amplitude detector 2 has a comparator 21 and a comparator 23. The gain control circuit 3 has a P-type MOS transistor 31 as a switching means 35, a P-type MOS transistor 32 as a switching means 35, a capacitor 33 and a resistor 34.
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