Double sampled biquad switched capacitor filter

Details Double sampled biquad switched capacitor filter Double sampled biquad switched capacitor filter

1993-04-06

1996-02-27

Sikes, William L.

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

Unwanted signal suppression

327561, H03B 100

Patent

active

054952000

ABSTRACT:
A biquad switched capacitor filter is preferably utilized as the output filter in a sigma delta digital-to-analog converter. The switched capacitor filter uses a cross-coupled switched capacitor circuit which delivers charge to the capacitors on both phases of the clock. As a result, the sizes of the capacitors can be reduced by a factor of two, while delivering the same charge as a single sampling circuit. By using the cross-coupled switching circuit everywhere in the filter, the sensitivity to capacitor mismatches is substantially reduced. The clock phases applied to the stages of the filter are alternated so that there is a one clock cycle delay around each loop containing two filter stages, thereby insuring the stability of the filter.

REFERENCES:
patent: 4574250 (1986-03-01), Senderowicz
patent: 4862121 (1989-08-01), Hochschild et al.
patent: 4920325 (1990-04-01), Nicollini et al.
Friedman, et al, "A Bit-Slice Architecture for Sigma-Delta Analog-to-Digital Converters," IEEE Journal on Selected Areas in Commuications vol. 6, No. 3, Apr. 1988, pp. 520-526.
Shih, et al, "Reference Refreshing Cyclic Analog-to-Digital and Digital-to-Analog Converters," IEEE Journal of Solid-State Circuits, vol. SC-21, No. 4, Aug. 1986, pp. 544-554.
Ribner et al, "Biquad Alternatives for High-Frequency Switched Capacitor Filters", IEEE J. Solid-State Circuits, vol. SC-20, No. 6, Dec. 1985, pp. 1085-1095.
Senderowicz et al, "A Family of Differential NMOS Analog Circuits for PCM Codec Filter Chip", IEEE J. Solid-State Circuits, vol. SC-17, No. 6, Dec. 1982, pp. 1014-1023.
Sarhang-Nejad et al, "A True 16-Bit 20 KHz Multibit .SIGMA..DELTA. ADC With Digital Correction", IEEE 1992 Custom Integrated Circuits Conf., pp. 16.4.1-16.4.4.

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