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Journal ArticleDOI

Programmable switched-capacitor filter with no additional silicon area

01 May 1984-Vol. 72, Iss: 5, pp 648-650
TL;DR: In this paper, a simple and economic method of programming the frequency response parameters of the switched-capacitor double-integrator biquad was presented, which yields considerable reduction in the capacitor spread and hence in silicon area.
Abstract: This letter reports a simple and economic method of programming the frequency-response parameters of the switched-capacitor double-integrator biquad It is shown that along with the programming facility, the scheme yields considerable reduction in the capacitor spread and hence in silicon area
Citations
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Journal ArticleDOI
TL;DR: In this paper, a systematic approach to the design of stray-insensitive switched-capacitor (SC) circuits from active-RC or RLC prototypes employing a parasitic insensitive SC differential voltage-controlled current-source as a basic building block is attempted.
Abstract: A systematic approach to the design of stray-insensitive switched-capacitor (SC) circuits from active-RC or RLC prototypes employing a parasitic insensitive SC differential voltage-controlled current-source as a basic building block is attempted. Procedures for transforming active-RC and RLC circuits into stray-insensitive SC circuits are formulated and illustrated with typical examples. Restrictions on the pole-frequency and pole-Q of the SC biquad are derived so that it closely emulates the frequency response of the original active-RC biquad. the SC biquad and the ladder filter derived by the proposed procedures were simulated with discrete components and tested in the laboratory. Test results agree closely with the theoretical predictions.

4 citations

References
More filters
Journal ArticleDOI
TL;DR: The filter is designed so that binary changes in the sampling frequency provide new sets of center frequencies which smoothly continue the logarithmic progression, and the accuracy and reproducibility inherent in the switched capacitor approach are retained.
Abstract: Techniques are presented for the design of a second-order switched capacitor filter which has its frequency response parameters programmed by the application of digital control signals. Two different types of weighted capacitor arrays are used to achieve programmability in the center frequency, peak gain, and selectivity. Experimental results are given for an integrated NMOS version with eight logarithmically-spaced center frequencies programmed by a 3 bit digital word, and 64 Q and gain values programmed by two 6 bit words. The filter is designed so that binary changes in the sampling frequency provide new sets of center frequencies which smoothly continue the logarithmic progression. Since the response depends on monolithic MOS capacitor ratios, the accuracy and reproducibility inherent in the switched capacitor approach are retained.

76 citations