| 摘要 |
PROBLEM TO BE SOLVED: To efficiently control an output in small steps in relation to gain adjustment of an amplifier circuit. SOLUTION: An output of an analog gain variable amplifier (PGA) 10 changing gain in predetermined steps is converted into digital data by an A/D converter 12. From the digital data output from the A/D converter 12, an output changed in smaller steps than the steps by the gain variable amplifier 10 is obtained by a small step changing part (+0.5 dB circuit) 14. Then, the output of the small step changing part 14 and the output of the A/D converter are selected by a selecting means (switch circuit) 16. Due to this, the output is controlled in smaller steps than the steps of the gain variable amplifier 10. COPYRIGHT: (C)2009,JPO&INPIT
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