Switched-current ladder band-pass filters

Queiroz, A.C. de; Pinheiro, P.M.

doi:10.1109/iscas.1994.409368

Cited by 8 publications

(5 citation statements)

References 6 publications

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“…The SC filter is derived from the passive prototype using well-known techniques [3,4,10,19]. The s-domain state-space equations of the ladder network are replaced by z-domain equations using the bilinear transform.…”

Section: Band-pass Sc Ladder Filtermentioning

confidence: 99%

“…The constants in (1-6) can be directly obtained from the passive components of the ladder network in Fig. 1 and from the sampling period [3,4]. In this design, the adopted sampling frequency was 200 kHz.…”

Section: Band-pass Sc Ladder Filtermentioning

confidence: 99%

“…Similarly to (1)(2)(3)(4)(5)(6), the coefficients of the transfer function (8) are expressed in terms of capacitance ratios, and there are also groups of ratios with the same denominator. According to (1)(2)(3)(4)(5)(6) and (8), the denominators of the capacitance ratios are composed by the feedback capacitances of the SC integrators, whereas the numerators are determined by the corresponding input capacitances of each integrator.…”

Section: Low-pass Biquad Filtermentioning

confidence: 99%

“…According to (1)(2)(3)(4)(5)(6) and (8), the denominators of the capacitance ratios are composed by the feedback capacitances of the SC integrators, whereas the numerators are determined by the corresponding input capacitances of each integrator. In general, state-space equations and transfer functions of SC filters have these properties [10], [32].…”

Section: Low-pass Biquad Filtermentioning

confidence: 99%

See 3 more Smart Citations

Using a Genetic Algorithm to Optimize Capacitance Ratio Approximations in SC Filters

Soares

Filho

Petraglia

2010

Circuits Syst Signal Process

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Accurate capacitance matching is one of the main design issues in switched-capacitor (SC) filters. Using identical unit capacitors in parallel to implement each filter capacitor, combined with a careful layout design, can provide an accuracy of 0.1% in the filter coefficients. The disadvantage of this technique is the fact that it can be directly applied only if the coefficients can be expressed as ratios of integer numbers. As a result, coefficient approximations are required, leading to frequency response errors. In this paper, a genetic algorithm (GA) is used to find the optimum capacitance ratio approximations by rational numbers that minimize the total number of unit capacitors for a given error tolerance in the frequency response. Design examples in 0.35 µm CMOS are presented and simulated to illustrate the proposed approach and verify its effectiveness.

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Section: Band-pass Sc Ladder Filtermentioning

confidence: 99%

Section: Band-pass Sc Ladder Filtermentioning

confidence: 99%

Section: Low-pass Biquad Filtermentioning

confidence: 99%

Section: Low-pass Biquad Filtermentioning

confidence: 99%

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Using a Genetic Algorithm to Optimize Capacitance Ratio Approximations in SC Filters

Soares

Filho

Petraglia

2010

Circuits Syst Signal Process

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“…1, was obtained from well-known synthesis techniques [7], using the elliptic approximation. The SC filter was derived from the passive prototype, using the design procedure described in [8] for switched-current filters. Following that design procedure, the bilinear transform was applied to the spacestate equations of the passive prototype.…”

Section: Band-pass Switched-capacitor Filtermentioning

confidence: 99%

An approximation algorithm to improve capacitance matching in the design of SC filters

Soares

Petraglia

2008

Analog Integr Circ Sig Process

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A critical issue in the design of switchedcapacitor (SC) filters is the capacitance matching, because the filter coefficients depend on capacitance ratios. The most successful design method to achieve an accurate capacitance matching employs a parallel arrangement of identical unit capacitors to implement each filter capacitor. However, this procedure can be directly applied only if the filter coefficients can be written as rational numbers, since each capacitor is implemented as an integer number of unit capacitors in parallel. This paper presents a systematic procedure, with low computational effort, to approximate the filter coefficients by integer ratios causing acceptable errors in the filter frequency response, whereas keeping the total number of unit capacitors small, in order to save die area. This procedure was applied in the design of a sixthorder SC band-pass filter, which has been fabricated in a 0.35 lm CMOS technology. The fabricated filter occupies an area of 0.913 mm 2 , exhibits low sensitivity to fabrication process deviations and has an output dynamic range of 79.2 dB.

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