Design of a general biquadratic filter section with only transconductances and grounded capacitors

Tan, M.A.; Schaumann, R.

doi:10.1109/31.1770

Cited by 28 publications

(13 citation statements)

References 9 publications

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“…Figure 4 shows the corresponding FGCER defined as [45]: Figure 5 shows the approximate value of FGCER obtained from (70) and (72) denoted by the solid line versus the exact value of FGCER (denoted by points) obtained by integration of nonlinear differential system (1), (2), describing the filter in question. The results are obtained for input signal amplitude V i = 0.7.…”

Section: Examplesmentioning

confidence: 99%

Analysis of OTA‐C filters with weakly nonlinear transconductors

Koziel

2007

Circuit Theory & Apps

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SUMMARYAn efficient approach for analysis of nonlinear distortion in OTA-C filters with weakly nonlinear transconductors is presented. The procedure is developed based on an algebraic description of a general OTA-C filter structure and, therefore, the results are valid for any filter architecture within OTA-C class. On the basis of the proposed method, explicit formulas for calculating a gain compression/expansion ratio in an arbitrary OTA-C filter are developed. The formulas are easy to implement and use in computer-aided filter design tools. For illustration purposes, several filter structures are considered. The accuracy of the method is verified by comparing the results with the exact values of gain compression/expansion ratio achieved by integrating the differential system that determines the time response of OTA-C filter. The presented approach can be generalized in order to consider other nonlinear parameters.

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Section: Examplesmentioning

confidence: 99%

Analysis of OTA‐C filters with weakly nonlinear transconductors

Koziel

2007

Circuit Theory & Apps

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“…The required "shape" of gin3 can, in principle, be found from (8). But Vex is a solution of a sixth-order nonlinear equation, and, as a result, (8) is difficult to solve.…”

Section: The Practical Designmentioning

confidence: 99%

Design considerations for CMOS and GaAs OTAs: Frequency response, linearity, tuning, and common-mode feedback

Schaumann

1991

Analog Integr Circ Sig Process

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High-performance operational transconductance amplifiers (OTAs) are important in the design of highfrequency analog transconductance-C (gin-C) filters. Critical design considerations for OTAs are frequency response, linearity, tuning, output impedance, power supply rejection (PSR), and common-mode rejection (CMR). In CMOS technology, satisfactory OTA design techniques are available, except that the linear input range often is relatively small and the frequency response of the OTA is limited by the intrinsic speed of transistors. In this paper, a new approach is developed to increase the linear input range, and a trade-off between linearity and input range is discussed. A CMOS OTA with less than +0.4% linearity error over a very large input range is given as a design example. To achieve a very high frequency response, l~m depletion-mode GaAs MESFETs with high intrinsic speed are used to replace MOSFETs. Simple ac compensation, a new technique for output impedance enhancement, and a new tuning method for OTAs with all N-channel devices are used to design a GaAs OTA with very small parasitics and f-3JB = 7 GHz. To improve PSR and CMR, fully balanced structures are used for the OTAs. Design considerations for the interaction of the operation of common-mode feedback (CMF) and tuning are discussed, and improved CMF circuits are proposed. Using the GaAs OTA and considering the frequency limitations imposed by parasitics, the design of a high order ladder filter with 300MHz cutoff frequency is presented as an application.

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“…For example, the standard Tow-Thomas structure that provides both a lowpass and a band-pass biquadratic transfer function has only two nodes (including the outputs) and grounded capacitors are connected at both of them; a simple and effective way of minimizing the effect of parasitic capacitances associated with those nodes is to subtract their (estimated) value from the (calculated) value of the placed capacitors. Most of the universal biquads reported so far have a more complicated structure, comprising at least one node without a placed capacitance [1], [2], [3], [4]; the parasitics associated with those nodes can degrade significantly the performance of the biquads, they can even change the nature of their transfer functions. As the impact of this issue is rarely discussed in the literature, two examples are analyzed briefly in Section II.…”

Section: Introductionmentioning

confidence: 99%

A new OTA-C universal biquad resonates out the main parasitic capacitance

Onet

Ţopa

2009

2009 European Conference on Circuit Theory and Design

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This paper proposes a core structure that provides, with minimum of adjustments, a wide range of second-order transfer functions, from the usual low-pass and band-pass to transfer functions with imaginary and complex zeroes. This universal biquad is implemented with transconductors and grounded capacitors. The performances of similar structures reported in the literature are significantly degraded by the parasitic capacitances present at their internal modes, especially those nodes without a placed capacitance. The biquad proposed here provides a way of resonating out the main parasitic capacitance, pushing most of its effects out of the band of interest. A design example demonstrates that this structure is suitable for the implementation of integrated filters operating in the tens of MHz frequency range.

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Design of a general biquadratic filter section with only transconductances and grounded capacitors

Cited by 28 publications

References 9 publications

Analysis of OTA‐C filters with weakly nonlinear transconductors

Analysis of OTA‐C filters with weakly nonlinear transconductors

Design considerations for CMOS and GaAs OTAs: Frequency response, linearity, tuning, and common-mode feedback

A new OTA-C universal biquad resonates out the main parasitic capacitance

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