| 摘要 |
There is provided an AGC circuit that has a very small offset voltage and is easy for integration, without using any of external capacities. For that reason, a variable gain amplifying circuit (GCA1) which has a gain controlled by a gain control signal, and whose output DC offset is controlled by an offset compensation signal, an A/D conversion circuit (AD1) for A/D converting an output signal of this variable gain amplifying circuit (GCA1), a level detection circuit (Det1) for performing peak detection of an output signal of this A/D conversion circuit (AD1) to thereby detect an amplitude level, a gain control circuit (Gctrl1) for outputting a gain control signal according to an output signal of this level detection circuit (Det1), an offset detection circuit (Det2) provided with a lowpass filter for taking out a DC component from the output signal of the A/D conversion circuit (AD1), and a D/A conversion circuit (DA1) for D/A converting an output signal of the offset detection circuit (Det2) to thereby output the offset compensation signal are provided.
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