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We address the practical problem of determining the loop filter component values in a single-loop continuous-time delta sigma modulator. Conventional techniques to design center the converter to achieve a desired noise transfer function are cumbersome and not numerically stable. We present a robust procedure that can be used to determine the loop filter coefficients when real opamps (with finite gain, arbitrary Digital to Analog Converter (DAC) pulse, and multiple internal poles/zeros) are used. The method can also account for excess loop delay. We illustrate our technique with second-order low-pass and fourth-order bandpass examples.
Circuits and Systems II: Express Briefs, IEEE Transactions on (Volume:57 , Issue: 3 )
Date of Publication: March 2010