| US 7,532,138 B2 | ||
| Delta-sigma modulator and DA converter apparatus including delta-sigma modulator changing order of filter | ||
| Taiji Akizuki, Miyagi (Japan); Tomoaki Maeda, Kyoto (Japan); and Masahiko Sagisaka, Osaka (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Filed on Feb. 21, 2008, as Appl. No. 12/35,344. | ||
| Claims priority of application No. 2007-040850 (JP), filed on Feb. 21, 2007. | ||
| Prior Publication US 2008/0198050 A1, Aug. 21, 2008 | ||
| Int. Cl. H03M 3/00 (2006.01) | ||
| U.S. Cl. 341—143 [341/155] | 13 Claims |
| 1. A delta-sigma modulator comprising:
a first subtractor for subtracting an inputted second input signal from an inputted first input signal, and outputting an
analog signal representing a subtraction result of the first subtractor;
a first integrator for integrating the analog signal outputted from the first subtractor, and outputting an integrated analog
signal;
a second subtractor for subtracting a sum of an inputted third analog signal and an inputted fourth analog signal from the
analog signal outputted from the first integrator, and outputting an analog signal representing a subtraction result of the
second subtractor;
a second integrator integrating the analog signal outputted from the second subtractor, and outputting an integrated analog
signal;
a quantizer for quantizing the analog signal outputted from the second integrator into a digital signal, and outputting the
digital signal;
a DA converter for DA-converting the digital signal outputted from the quantizer into an analog signal, and outputting the
analog signal;
a first feedback circuit including a plurality of first charge holding circuits for holding electric charges of the analog
signal outputted from the DA converter for different sampling intervals, respectively, the first feedback circuit capable
of changing a feedback amount of the analog signal outputted from the DA converter, and outputting the analog signal from
each of the first charge holding circuits to the second subtractor as a third analog signal;
a second feedback circuit including a plurality of second charge holding circuits for holding electric charges of the analog
signal outputted from the second integrator for different sampling intervals, respectively, the second feedback circuit capable
of changing a feedback amount of the analog signal outputted from the second integrator, and outputting an analog signal from
each of the second charge holding circuits to the second subtractor as a fourth analog signal, and
a controller for switching an order of a filter of a filter characteristic of the delta sigma modulator by changing feedback
amounts of the first and second feedback circuits.
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