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Willy Sansen - One of the best experts on this subject based on the ideXlab platform.
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simulation based generation of posynomial performance models for the sizing of Analog Integrated Circuits
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 2003Co-Authors: Walter Daems, Georges Gielen, Willy SansenAbstract:This paper presents an overview of methods to automatically generate posynomial response surface models for the performance characteristics of Analog Integrated Circuits based on numerical simulation data. The methods are capable of generating posynomial performance expressions for both linear and nonlinear Circuits and circuit characteristics, at SPICE-level accuracy. This approach allows for automatic generation of an accurate sizing model for a circuit that composes a geometric program that fully describes the Analog circuit sizing problem. The automatic generation avoids the time-consuming and approximate nature of handcrafted analytic model generation. The methods are based on techniques from design of experiments and response surface modeling. Attention is paid to estimating the relative "goodness-of-fit" of the generated models. Experimental results illustrate the capabilities and effectiveness of the presented methods.
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an efficient optimization based technique to generate posynomial performance models for Analog Integrated Circuits
Design Automation Conference, 2002Co-Authors: Walter Daems, Georges Gielen, Willy SansenAbstract:This paper presents an new direct--fitting method to generate posynomial response surface models with arbitrary constant exponents for linear and nonlinear performance parameters of Analog Integrated Circuits. Posynomial models enable the use of efficient geometric programming techniques for circuit sizing and optimization. The automatic generation avoids the time--consuming nature and inaccuracies of handcrafted analytic model generation. The technique is based on the fitting of posynomial model templates to numerical data from SPICE simulations. Attention is paid to estimating the relative `goodness--of--fit' of the generated models. Experimental results illustrate the significantly better accuracy of the new approach.
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amgie a synthesis environment for cmos Analog Integrated Circuits
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 2001Co-Authors: G. Van Der Plas, Willy Sansen, Georges Gielen, K Lampaert, G Debyser, F Leyn, J Vandenbussche, P Veselinovic, D LeenartsAbstract:A synthesis environment for Analog Integrated Circuits is presented that is able to drastically increase design and layout productivity for Analog blocks. The system covers the complete design flow from specification over topology selection and optimal circuit sizing down to automatic layout generation and performance characterization. It follows a hierarchical refinement strategy for more complex cells and is process independent. The sizing is based on an improved equation-based optimization approach, where the circuit behavior is characterized by declarative models that are then converted in a sequential design plan. Supporting tools have been developed to reduce the total effort to set up a new circuit topology in the system's database. The performance-driven layout generation tool guarantees layouts that satisfy all performance constraints. Redesign support is included in the design flow management to perform backtracking in case of design problems. The experimental results illustrate the productiveness and efficiency of the environment for the synthesis and process tuning of frequently used Analog cells.
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High-frequency distortion analysis of Analog Integrated Circuits
IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, 1999Co-Authors: P Wambacq, G.g.e. Gielen, P.r. Kinget, Willy SansenAbstract:An approach is presented for the analysis of the nonlinear behavior of Analog Integrated Circuits. The approach is based on a variant of the Volterra series approach for frequency domain analysis of weakly nonlinear Circuits with one input port, such as amplifiers, and with more than one input port, such as Analog mixers and multipliers. By coupling numerical results with symbolic results, both obtained with this method, insight into the nonlinear operation of Analog Integrated Circuits can be gained. For accurate distortion computations, the accuracy of the transistor models is critical. A MOS transistor model is discussed that allows us to explain the measured fourth-order nonlinear behavior of a 1 GHz CMOS upconverter. Further, the method is illustrated with several examples, including the analysis of an operational amplifier up to its gain-bandwidth product. This example has also been verified experimentally.
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symbolic network analysis methods for practical Analog Integrated Circuits a survey
IEEE Transactions on Circuits and Systems Ii: Analog and Digital Signal Processing, 1998Co-Authors: P Wambacq, Georges Gielen, Willy SansenAbstract:A comparative study of symbolic network analysis methods for Analog Integrated Circuits of practical size is presented. The methods are compared with respect to two important criteria: (1) the running time limits of the different algorithms used within every method and (2) the number of terms that are generated needlessly; i.e., generated invalid terms and cancelling terms. The methods are compared for several Analog Integrated building blocks. The results indicate that conclusions about the efficiency of the different symbolic analysis methods based upon comparisons for small Circuits, can be misleading. The study also allows the reader to make a good choice for a symbolic analysis method as the core routine of a modern symbolic analyzer with symbolic simplification capabilities.
Georges Gielen - One of the best experts on this subject based on the ideXlab platform.
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Techniques and Applications of Symbolic Analysis for Analog Integrated Circuits: A Tutorial Overview
Computer-Aided Design of Analog Integrated Circuits and Systems, 2020Co-Authors: Rob A. Rutenbar, Georges Gielen, Brian A. AntaoAbstract:This tutorial paper gives an overview of the state of the art in symbolic analysis techniques for Analog Integrated Circuits. Symbolic analysis allows to generate closed-form analytic expre-ssions for a circuit's small-signal characteristics with the circuit's elements and the frequency variable represented by symbols. Such analytic information complements the results from numerical simulations. The paper then describes the different application areas of symbolic analysis in the design of Analog Integrated Circuits. Symbolic analysis is mainly used as a means to obtain insight into a circuit's behavior, to generate analytic models for automated circuit sizing, for behavioral model generation and in applications requiring the repetitive evaluation of circuit characteristics. Recent extensions of both the functionality (such as towards symbolic distortion or pole-zero analysis) and the efficiency of symbolic analysis for larger Circuits (through new algorithmic developments) are discussed. Finally, an overview and comparison of existing tools is presented.
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Symbolic Distortion Analysis of Analog Integrated Circuits
2020Co-Authors: Wim Verhaegen, Georges GielenAbstract:A technique for generating symbolic expressions for the distortion in weakly nonlinear Analog Integrated Circuits is presented. This technique uses some acceptable assumptions to reduce the task of analyzing the nonlinear circuit to a repeated analysis of derived linear Circuits. This repetitive algorithm has been implemented and it is demonstrated on an example circuit. In the analysis of Analog Integrated Circuits, distortion and intermodulation are important factors. Either they are unwanted, as is the case in linear building blocks like opamps, or they are explicitly wanted to obtain a signal shifted in frequency, as is the case with mixers. Distortion and intermodulation need to be assessed ac- curately in both cases. Classical numerical simulation techniques using it- erative algorithms for solving the differential equations are slow and inaccurate due to the large difference be- tween the time constants normally present in the Circuits of interest. Several numerical methods have been devel- oped to overcome this problem, e.g. the harmonic bal- ance technique (1), multitime analysis (2) and the use of describing functions in Circuits with feedback (3). How- ever, the numerical nature of these techniques implies that no symbolic results can be derived, so that re-use of results — in the form of design equations — is not possible. An analysis technique that does yield symbolic re- sults is described in this paper. Based on a set of as- sumptions, the analysis of a weakly nonlinear circuit is reduced to a number of analyses of linear Circuits. A lin- ear symbolic analysis core is used for these individual analysis steps, and its results are combined and manip- ulated to get a closed-form symbolic end result. This result can be used as a design equation, or the impact of the circuit nonlinearities on distortion and intermodula- tion can be derived from it. Before explaining this technique, it is to be noted that similar approaches have been followed in the past to obtain symbolic expressions for the distortion in spe- cific classes of Circuits. E.g. the distortion in sampling mixers is analyzed in (4), and a method for analyzing the distortion in Analog building blocks is presented in (5). All symbolic approaches are intrinsically limited someway, and these publications are no exceptions. The scope of the algorithm presented in this paper is limited to weakly nonlinear Circuits. This means that the circuit
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globally reliable variation aware sizing of Analog Integrated Circuits via response surfaces and structural homotopy
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 2009Co-Authors: Trent Mcconaghy, Georges GielenAbstract:This paper presents SANGRIA, a tool for automated globally reliable variation-aware sizing of Analog Integrated Circuits. Its keys to efficient search are adaptive response surface modeling, and a new concept, structural homotopy. Structural homotopy embeds homotopy-style objective function tightening into the search state's structure, not dynamics. Searches at several different levels are conducted simultaneously: The loosest level does nominal dc simulation, and tighter levels add more analyses and {process, environmental} corners. New randomly generated designs are continually fed into the lowest (cheapest) level, always trying new regions to avoid premature convergence. For further efficiency, SANGRIA adaptively constructs response surface models, from which new candidate designs are optimally chosen according to both yield optimality on model and model prediction uncertainty. The stochastic gradient boosting models support arbitrary nonlinearities, and have linear scaling with input dimension and sample size. SANGRIA uses SPICE in the loop, supports accurate/complex statistical SPICE models, and does not make assumptions about the convexity or differentiability of the objective function. SANGRIA is demonstrated on four different Analog Circuits having from 10 to 50 devices and up to 444 design/process/environmental variables.
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a memetic approach to the automatic design of high performance Analog Integrated Circuits
ACM Transactions on Design Automation of Electronic Systems, 2009Co-Authors: F.v. Fernandez, Georges Gielen, R Castrolopez, E RocaAbstract:This article introduces an evolution-based methodology, named memetic single-objective evolutionary algorithm (MSOEA), for automated sizing of high-performance Analog Integrated Circuits. Memetic algorithms may achieve higher global and local search ability by properly combining operators from different standard evolutionary algorithms. By integrating operators from the differential evolution algorithm, from the real-coded genetic algorithm, operators inspired by the simulated annealing algorithm, and a set of constraint handling techniques, MSOEA specializes in handling Analog circuit design problems with numerous and tight design constraints. The method has been tested through the sizing of several Analog Circuits. The results show that design specifications are met and objective functions are highly optimized. Comparisons with available methods like genetic algorithm and differential evolution in conjunction with static penalty functions, as well as with intelligent selection-based differential evolution, are also carried out, showing that the proposed algorithm has important advantages in terms of constraint handling ability and optimization quality.
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simulation based generation of posynomial performance models for the sizing of Analog Integrated Circuits
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 2003Co-Authors: Walter Daems, Georges Gielen, Willy SansenAbstract:This paper presents an overview of methods to automatically generate posynomial response surface models for the performance characteristics of Analog Integrated Circuits based on numerical simulation data. The methods are capable of generating posynomial performance expressions for both linear and nonlinear Circuits and circuit characteristics, at SPICE-level accuracy. This approach allows for automatic generation of an accurate sizing model for a circuit that composes a geometric program that fully describes the Analog circuit sizing problem. The automatic generation avoids the time-consuming and approximate nature of handcrafted analytic model generation. The methods are based on techniques from design of experiments and response surface modeling. Attention is paid to estimating the relative "goodness-of-fit" of the generated models. Experimental results illustrate the capabilities and effectiveness of the presented methods.
W. Sansen - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of error-control strategies for the linear symbolic analysis of Analog Integrated Circuits
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1999Co-Authors: W. Daems, W. Verhaegen, P. Wambacq, G. Gielen, W. SansenAbstract:The generation of approximate linear symbolic expressions for Analog Integrated Circuits requires the use of an appropriate error-control strategy. The error-control strategy determines both correctness and compactness of the approximate expression. This paper presents an evaluation of different error-control strategies that fit within the flat symbolic analysis, using simplification during generation techniques for large Analog Integrated Circuits. The theoretical exposition is illustrated with experimental results that allow a comparison of the proposed methods.
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Toward sub 1 V Analog Integrated Circuits in submicron standard CMOS technologies
1998 IEEE International Solid-State Circuits Conference. Digest of Technical Papers ISSCC. First Edition (Cat. No.98CH36156), 1998Co-Authors: W. Sansen, M. Steyaert, V. Peluso, E. PeetersAbstract:Lower channel lengths lead to lower supply voltages. For 0.25 /spl mu/m MOSTs the supply voltage is 2.5 V. Even lower supply voltages will follow. This paper deals with Analog Integrated Circuits that can handle the reduction of the supply voltage down to 1 V. Existing solutions for such low supply voltages are: 1) reduction of threshold voltages from 0.7 V to 0.3-0.4 V; 2) use of voltage multipliers. It is possible to reduce supply voltages to 1 V in standard CMOS without voltage multipliers. The advent of deep submicron CMOS dictates reduced supply voltage.
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Efficient symbolic computation of approximated small-signal characteristics of Analog Integrated Circuits
IEEE Journal of Solid-State Circuits, 1995Co-Authors: P. Wambacq, F.v. Fernandez, G. Gielen, W. Sansen, A. Rodriguez-vazquezAbstract:A symbolic analysis tool is presented that generates simplified symbolic expressions for the small-signal characteristics of large Analog Integrated Circuits. The expressions are approximated while they are computed, so that only those terms are generated which remain in the final expression. This principle causes drastic savings in CPU time and memory, compared with previous symbolic analysis tools. In this way, the maximum size of Circuits that can be analyzed, is largely increased. By taking into account a range for the value of a circuit parameter rather than one single number, the generated expressions are also more generally valid. Mismatch handling is explicitly taken into account in the algorithm. The capabilities of the new tool are illustrated with several experimental results.
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Symbolic analysis of large Analog Integrated Circuits by approximation during expression generation
Proceedings of IEEE International Symposium on Circuits and Systems - ISCAS '94, 1994Co-Authors: F.v. Fernandez, A. Rodriguez-vazquez, P. Wambacq, G. Gielen, W. SansenAbstract:A novel algorithm is presented that generates approximate symbolic expressions for small-signal characteristics of large Analog Integrated Circuits. The method is based upon the approximation of an expression while it is being computed. The CPU time and memory requirements are reduced drastically with regard to previous approaches, as only those terms are calculated which will remain in the final expression. As a consequence, the maximum circuit size amenable to symbolic analysis has largely increased. The simplification procedure explicitly takes into account variation ranges of the symbolic parameters to avoid inaccuracies of conventional approaches which use a single value. The new approach is also able to take into account mismatches between the symbolic parameters.
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A design tool for weakly nonlinear Analog Integrated Circuits with multiple inputs (mixers, multipliers)
Proceedings of the IEEE 1991 Custom Integrated Circuits Conference, 1991Co-Authors: P. Wambacq, G. Gielen, J. Vanthienen, W. SansenAbstract:A software package is presented that generates symbolic or numerical results for gain, noise, and distortion behavior of weakly nonlinear Analog Integrated Circuits with multiple inputs. The program provides insight into the behavior of mixers, multipliers, and AGC amplifiers. This analysis tool is part of the symbolic simulator ISAAC, and it can reduce the design time of the above-mentioned Circuits by giving insight into conversion gain, intermodulation distortion, and noise that mixes with signals. Analytic expressions make it possible to identify the dominant parameters that determine the circuit's nonlinear behavior.
W.a. Serdijn - One of the best experts on this subject based on the ideXlab platform.
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Design principles for low-voltage low-power Analog Integrated Circuits
2001 IEEE International Symposium on Circuits and Systems (ISCAS), 2001Co-Authors: W.a. SerdijnAbstract:Design strategies for Analog Integrated Circuits for the reduction of stochastic errors and systematic errors are normally not consistent with design strategies which take into account power dissipation, voltage range and current range. The combination of transfer quality, low voltage and low power must be considered during the whole design process.
J.l. Huertas - One of the best experts on this subject based on the ideXlab platform.
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Practical solutions for the application of the oscillation-based-test in Analog Integrated Circuits
2002 IEEE International Symposium on Circuits and Systems. Proceedings (Cat. No.02CH37353), 2002Co-Authors: D. Vazquez, G. Huertas, G. Leger, A. Rueda, J.l. HuertasAbstract:This paper presents practical solutions for solving the problems arising when applying the oscillation-based-test to Analog Integrated Circuits. It is devoted to discussing a practical on-chip evaluation of the generated test signals. The required circuitry is very simple and robust. Moreover, preliminary results obtained from an Integrated prototype are also included.
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ASAP: a portable program for the symbolic analysis of Analog Integrated Circuits
[Proceedings] EURO ASIC `90, 1990Co-Authors: F.v. Fernandez, A. Rodriguez-vazquez, J.l. HuertasAbstract:A new and efficient symbolic analyzer for Analog Integrated Circuits, ASAP (Analog Symbolic Analysis Program), is presented. ASAP provides symbolic expressions for all types of AC transfer and driving-point characteristics of Analog Integrated Circuits. The resulting expressions can be automatically simplified, which makes them useful for circuit synthesis. The main features of the program are described as well as some illustrative examples showing the usefulness and efficiency of the program.