| 摘要 |
PURPOSE:To attain miniaturization of the titled converter, low cost and power saving by detecting envelope information from a digital input signal so as to control a conversion coefficient of a multiplication type D/A converter and extracting an analog output signal from the output of the said D/A converter. CONSTITUTION:An input digital input signal from an input terminal 20 is subjected to frequency conversion by a sampling frequency converter 22 and its envelope information is detected by an envelope information detecting means such as a detector 25. The envelope information is fed to a D/A converter 21, which changes the conversion coefficient based on the envelope information. Then an analog output signal is outputted to an output terminal 28 via a low pass filter 52 and a frequency converting circuit 53 or the digital input signal fed directly is expanded and D/A-converted. The expander function and D/A converting function are unified to form a CMOS IC, then the IC incorporating the expander and the D/A converter is attained.
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