| 摘要 |
PURPOSE:To control exactly a control circuit even if the input level of an A/D converter is high, by holding only the digital signal of an outside in a holding circuit, and sending it out as a control signal to an integrator. CONSTITUTION:When an analog signal is inputted to an A/D converter 1, whether it is in the outside of a Path 2 or not is decided. When it is in the outside of an arrow (a) or (b), a selecting circuit 52 sends a signal to a holding circuit 51, makes the circuit 51 hold the signal of its outside and uses it as a control signal. This control signal is inputted to the weighting circuit 23 of a variable gain amplifier 2 through an integrator 3. Also, a CLK from a phase shifter 4 which is used for a control signal generating circuit is effective only when the signal is in the above-mentioned outside. In this way, the signal of only the outside where the variation of an input level is remarkable can be used as the control signal, therefore, the input level can be controlled exactly.
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