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On impedance evaluation in feedback circuits

IEEE TRANSACTIONS ON EDUCATION 2002年第4期45卷 371-379页

作者： Corsi, F Marzocca, C Matarrese, G Politen Bari Dept Elettrotecn & Elettron I-70125 Bari Italy

One of the main benefits of negative feedback is the ability to control the impedances in linear active networks (LANs). Traditionally in undergraduate courses, the design of a feedback circuit is cast in terms of a two-port analysis, since the closed-loop properties of the circuit are expressed in terms of the corresponding open-loop ones. Therefore, the designer can directly identify the proper feedback topology and adjust the amount of feedback based on the specified closed-loop performances. However, there are practical situations in which a two-port analysis may lead to incorrect results if applied inappropriately or cannot be applied at all. In this paper, the authors show how it is possible to achieve a better insight of these problems in the light of Blackman's method. Moreover, after a derivation of the formula as a consequence of the superposition principle applied to a LAN, they discuss, with reference to some typical examples, the conditions that must be met for the correct application of the two-port method.

关键词： Blackman's formula feedback circuits impedance evaluation return ratio two-port analysis

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ANALYSIS OF COMMUTATED NETWORKS EMPLOYING feedback circuits

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1969年第1期AES5卷 39-&页

作者： BORELLI, MT NASA Marshall Space Flight Center Huntsville AL USA

A method of analysis has been developed for feedback systems employing commutated networks in the forward loop and linear transfer functions in the feedback loop. The method handles single-phase and polyphase commutated networks as well as coupled and uncoupled networks. Although commutated networks are linear from the superposition theory viewpoint, linear feedback theory is shown to be not applicable because of the harmonics present in the feedback loop. Techniques for simplifying the analysis of commutated networks by the use of equivalent block diagrams provide additional insights into commutated network operation.

关键词： feedback circuits feedback loop Frequency Power harmonic filters Switches Band pass filters Magnetic separation Control systems Transfer functions Coupling circuits

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Determination of stability using return ratios in balanced fully differential feedback circuits

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IEEE TRANSACTIONS ON circuits AND SYSTEMS II-ANALOG AND DIGITAL SIGNAL PROCESSING 1995年第12期42卷 805-817页

作者： Hurst, PJ Lewis, SH Department of Electrical and Computer EngineeringCircuits Research Laboratory University of California Davis CA USA

This paper describes SPICE [1] simulation techniques that can be used to find the return ratios for the differential and common-mode feedback loops in balanced, fully differential circuits, Since each of these loops may contain multiple feedback paths, conditions under which these two return ratios are sufficient for determining stability of the balanced feedback circuit are described, To allow the use of these techniques with switched-capacitor common-mode feedback circuits, a special simulation technique is presented that finds the de bias for the return-ratio simulations.

关键词： Circuit stability feedback circuits Circuit simulation Operational amplifiers feedback loop Delta modulation Impedance SPICE Switching circuits Stability analysis

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IMPROVING PERFORMANCE OF DIGITAL SINUSOIDAL OSCILLATORS BY MEANS OF ERROR feedback-circuits

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IEEE TRANSACTIONS ON circuits AND SYSTEMS 1986年第4期33卷 373-380页

作者： ABUELHAIJA, AI ALIBRAHIM, MM YARMOUK UNIV DEPT ELECT ENGNIRBIDJORDAN

A few structures for digital sinusoidal oscillators have been proposed, together with the design methods used for such structures. Because of the finite wordlength effects, these structures produce high roundoff errors which change both the amplitude and frequency of the generated sinusoidal signal. This makes it difficult to design an oscillator which generates a sinusoidal waveform with a particular frequency and amplitude. It is shown in this paper that if we add to the direct form digital oscillator a circuit which saves the quantization error and feeds it back for consideration at subsequent iterations, roundoff errors are considerably reduced, and the frequency and amplitude of the generated waveform are very close to those expected by theory. Formulas are derived for the resulting errors and simulation results are given, showing that a significant improvement is obtained by error feedback.

关键词： Oscillators feedback circuits Frequency Roundoff errors Design methodology Finite wordlength effects Signal generators Quantization Feeds Circuit simulation

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Synthetic negative feedback circuits using engineered small RNAs

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NUCLEIC ACIDS RESEARCH 2018年第18期46卷 9875-9889页

作者： Kelly, Ciaran L. Harris, Andreas W. K. Steel, Harrison Hancock, Edward J. Heap, John T. Papachristodoulou, Antonis Univ Oxford Dept Engn Sci Parks Rd Oxford OX1 3PJ England Imperial Coll London Dept Life Sci Imperial Coll Ctr Synthet Biol South Kensington Campus London SW7 2AZ England Newcastle Univ Sch Nat & Environm Sci Newcastle NE1 7RU England Univ Sydney Sch Math & Stat Sydney NSW 2006 Australia Univ Sydney Charles Perkins Ctr Sydney NSW 2006 Australia

Negative feedback is known to enable biological and man-made systems to perform reliably in the face of uncertainties and disturbances. To date, synthetic biological feedback circuits have primarily relied upon protein-based, transcriptional regulation to control circuit output. Small RNAs (sRNAs) are non-coding RNA molecules that can inhibit translation of target messenger RNAs (mRNAs). In this work, we modelled, built and validated two synthetic negative feedback circuits that use rationally-designed sRNAs for the first time. The first circuit builds upon the well characterised tet-based autorepressor, incorporating an externally-inducible sRNA to tune the effective feedback strength. This allows more precise fine-tuning of the circuit output in contrast to the sigmoidal, steep input-output response of the autorepressor alone. In the second circuit, the output is a transcription factor that induces expression of an sRNA, which inhibits translation of the mRNA encoding the output, creating direct, closed-loop, negative feedback. Analysis of the noise profiles of both circuits showed that the use of sRNAs did not result in large increases in noise. Stochastic and deterministic modelling of both circuits agreed well with experimental data. Finally, simulations using fitted parameters allowed dynamic attributes of each circuit such as response time and disturbance rejection to be investigated.

关键词： Output Disturbance rejection feedback circuits Untranslated RNA Transcription Factors negative feedback circuits Negative feedback

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ON THE EQUIVALENCE OF NONLINEAR POSITIVE feedback-circuits TO CONSTRAINED ITERATIVE SIGNAL RECONSTRUCTION ALGORITHMS

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IEEE TRANSACTIONS ON circuits AND SYSTEMS II-ANALOG AND DIGITAL SIGNAL PROCESSING 1993年第7期40卷 455-457页

作者： TARATORIN, AM SIDEMAN, S Heart System Research Center The Julius Silver Institute Department of Biomedical Engineering Technion-Israel Institute of Technology Haifa Israel

Constrained nonlinear iterative algorithms for signal restoration and reconstruction from zero crossings or clipped signals have a common structure of iterations and can be written as an infinite nonlinear operator series. This operator series corresponds to an analog nonlinear positive feedback circuit: the signal transformation, after an infinite number of iterations, is equivalent to the signal obtained by passing through the nonlinear instantaneous positive-feedback analog circuit. The corresponding structures of the feedback circuits for two reconstruction algorithms are presented. This interpretation offers interesting possibilities for real time signal reconstruction.

关键词： feedback circuits Signal reconstruction Iterative algorithms Signal restoration Nonlinear distortion Nonlinear filters Analog circuits Reconstruction algorithms Absorption Heart

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THE ROLE OF feedback-circuits - POSITIVE feedback-circuits ARE A NECESSARY CONDITION FOR POSITIVE REAL EIGENVALUES OF THE JACOBIAN MATRIX

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BERICHTE DER BUNSEN-GESELLSCHAFT-PHYSICAL CHEMISTRY CHEMICAL PHYSICS 1994年第9期98卷 1148-1151页

作者： THOMAS, R Laboratoire de Génétique Faculté des Sciences Université Libre de Bruxelles Rue des Chevaux 67 B‐1640 Rhode‐St.‐Genèse Belgium

This talk deals with the biological roles of feedback loops and their combinations. It has progressively become clear that a negative loop is a necessary (not sufficient) condition for a stable periodic behaviour and that a positive loop is a necessary (not sufficient) condition for multistationarity. Of these old conjectures (e.g. Stud. phys. theor. Chem. 28, 307 (1983)), the second has now two formal demonstrations by others (Plahte et al., Snoussi). Here, we remark that this statement can be generalised as follows. The presence of a positive loop (in the Jacobian matrix of the system) is a necessary condition for having at least one real positive root in the characteristic equation (this can be shown to directly derive from the Descartes rule) and at least one real positive root in turn is a necessary condition for multistationarity.

关键词： feedback circuits JACOBIAN MATRIX MULTISTATIONARY NONLINEAR PHENOMENA

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EXPERIMENTAL INVESTIGATIONS OF feedback-circuits FOR SUPPRESSING RESISTIVE WALL MODES

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IEEE TRANSACTIONS ON PLASMA SCIENCE 1991年第5期19卷 954-958页

作者： PLATT, CL ROBERTSON, SH UNIV COLORADO DEPT ASTROPHYS PLANETARY & ATMOSPHER SCIBOULDERCO 80309

feedback circuits have been designed and tested which reduce the component of a fluctuating magnetic field normal to a square coil. These circuits, when placed in an array covering a toroidal plasma, may be a practica... 详细信息

关键词： feedback circuits Coils Detectors Frequency Circuit testing Toroidal magnetic fields Plasmas feedback control feedback amplifiers Intelligent sensors

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Deterministic chaos seen in terms of feedback circuits: Analysis, synthesis, "labyrinth chaos"

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INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS 1999年第10期9卷 1889-1905页

作者： Thomas, R Free Univ Brussels Lab Genet Procaryotes B-1050 Brussels Belgium Free Univ Brussels Ctr Nonlinear Phenomena & Complex Syst B-1050 Brussels Belgium

This paper aims to show how complex nonlinear dynamic systems can be classified, analyzed and synthesized in terms of feedback circuits. The Rossler equations for deterministic chaos are revisited and generalized in this perspective. It is shown that once a proper set of feedback circuits is present in the Jacobian matrix of the system, the chaotic character of trajectories is remarkably robust versus changes in the nature of the nonlinearities. "Labyrinth chaos", whereby simple differential systems generate large lattices of many unstable steady states embedded in a chaotic attractor, is constructed using this technique. In the limit case of a single three-element circuit without diagonal elements, one finds systems possessing an infinite lattice of unstable steady states between which trajectories percolate in a deterministic chaotic way.

关键词： feedback circuits deterministic trajectory chaos Jacobian matrix nonlinearity

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SOME STUDIES ON DELAYED feedback circuits

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PROCEEDINGS OF THE INSTITUTE OF RADIO ENGINEERS 1958年第4期46卷 758-763页

作者： SEKI, H Iwasaki Tsushinki Company Tokyo Japan

This paper attempts to describe a new method by which periodic signals in noise can be detected easily without the aid of an expensive correlator. In principle, the circuit consists of a delay network which is inserted as a part of a unidirectional loop connected with the main circuit through a hybrid coil. The delay time must be equal to, or an integral multiple of, the signal period to be detected. The delay time also must be longer than the inverse figure of the preceding network bandwidth. Successive noises will be superimposed one after another at random in circulation, while the signals are superimposed in phase. This means an improvement in the signal-to-noise ratio. Theoretically, the ideal basic delayed feedback circuit gives an improvement in the snr of 7.66 db, and in the apparent Q of 9.06. Further improvement can be expected by the use of active circuits. Possible applications are for producing artificial reverberation, a narrow-band filter, and a short-time memory circuit. The response of the delayed feedback circuit is like a comb filter. The circuit also can extract complicated periodic waves without an appreciable distortion.

关键词： feedback circuits Circuit noise Delay effects Filters Correlators Coils Bandwidth Phase noise Signal to noise ratio Active circuits

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