| 摘要 |
A D/A converting circuit comprises two data selectors and two D/A converters having an external reference input terminal. A decoder responsive to several bits including the MSB of the input digital signal to be converted into an analog signal is provided to detect whether the input digital signal represents an analog signal magnitude which is greater than the full-scale value of the analog signal or not, and thus expansion-nonexpansion operation of the D/A converting circuit is controlled so that an m-bit D/A converter can be used, as the first D/A converter, to handle an n-bit digital signal where n>m. The first D/A converter receives m-bit information including the MSB in expansion mode, and receives m-bit information including the LSB in nonexpansion mode. The second D/A converter receives K-bit information (K=n-m) including the LSB of the input digital signal in expansion mode, and receives a predetermined digital data from a fixed data circut in nonexpansion mode. The second D/A converter performs D/A conversion by using a fixed voltage, and the output analog voltage of the second D/A converter is added to the fixed voltage prior to being fed to the first D/A converter as its reference voltage when expansion is required.
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