Systematic Design of Linear HF CMOS Circuits

Researcher : Bruccoleri, F.

Supervisor(s) :

Project Duration : Dec 1, 1997 - Dec 1, 2001


Summary of the project

It is the aim of the project to show the usefulness of systematic circuit design methods for the design of linear HF CMOS circuits (in contrast to the usual largely intuitive human expert approach). A recently developed method for systematic circuit topology generation, classification and analysis will be used as a basis [12]. This method will be evaluated for practical HF design problems and extended to enhance its applicability. Attention will be paid to:

    • Systematic generation of alternative circuit topologies for linear HF circuits. Typical examples of circuits that can be designed using the method are broadband-amplifiers, AGC-amplifiers, Buffers, Transconductors and Trans-impedance amplifiers.
    • The development of a sizing strategy (choosing component values) to establish correct DC-biasing in circuits and/or satisfy a given set of design requirements. Hierarchical symbolic macro-models, developed in [12], will be used for first-cut design. Furthermore, as large numbers of circuits are involved, use will be made of automatic circuit optimisation tools.
    • The extension of existing behavioural macro-models to include important MOS-device properties like the finite output resistance, the back-gate effect and capacitive effects.
    • The validation of the design method and modelling by design experiments.

It is expected that the project will render results in two main fields:

    • Systematic design methodology, which is useful for design automation and education.
    • High-performance circuit designs.

State-of-the-art in CMOS circuit design

CMOS technology is the main-stream technology for base-band digital signal processing for communication applications. However, integrated analog circuits for intermediate and high frequencies (typical frequencies ranging from several MHz to the GHz region) are of increasing importance in modern communication systems. Considerations of power dissipation, size and cost ask for a larger portion of the HF analog signal processing to be integrated with the digital baseband signal processing. For digital radio personal communication devices the bands between 800 MHz and 2.5 GHz play an increasingly important role. Optical communication links use frequencies extending well above 1 GHz. As the main technology used for a low-cost implementation of the required digital signal processing is CMOS, the design of analog HF circuits in CMOS is a hot research topic.

Linear HF two-port circuits are important building blocks for communication ICs (e.g. AGC-amplifiers, buffers in RC-based oscillators and poly-phase filters, transconductors for Transconductance-C filters, trans-impedance amplifiers, broadband-amplifiers). Such circuits are usually designed by experienced analog designers, using a largely intuitive design approach. Based on past experience, one or a few known circuit topologies are often re-used and adapted to fit a specific application. The HF circuit designs that result are typically very simple in terms of the number of devices. Apart from the elegance of simple solutions, there are some good reasons for this design practice: adding components tends to limit the high frequency potential of circuits (additional nodes introduce additional poles in the transfer function) and tends to increase the noise level and power consumption. Hence, "squeezing" maximal functionality out of a minimal set of components seems to be a viable design philosophy.

Although the intuitive design method has proven itself in practice, it has clear disadvantages:

  • Known circuit topologies are favoured, although there may be alternative circuit topologies that are more suitable. Moreover, in case a circuit does not satisfy the requirements, the intuitive approach does not give a clue for alternative solutions. Innovations in circuit topology are largely dependent on fortuitous bright ideas of designers.
  • It takes a long time for a designer to become "experienced", and it is not clear how an "intuitive design approach" should be taught to new designers. Furthermore, the intuitive approach is not very suitable for implementation in a CAD system for analog design.

Systematic Design Methods

These observations in the previous section argue for the development of design methodologies that explore the design space in a more systematic way. Systematic design approaches have the potential of improving the quality of design (less chance of overlooking interesting design options) and improving design efficiency (re-use of design knowledge and eventually possibly automation).

A recent PhD thesis [12] aims at a systematic design method for linear building blocks. It is shown that hundreds of alternative circuit topologies can be generated systematically (exhaustive graph based circuit topology generation), by using a voltage controlled current source to model a MOS transistor, a resistor, or combinations of these components. Moreover, these circuits are classified and analysed systematically. Alternative circuit implementations show specific strong and weak points, in various mixes, so that the best solution depends on the combination of requirements. Hence the availability of a set of alternative circuits seems to be very useful to fit different applications (different set of specifications) and different boundary conditions (IC-technology, supply voltage).


Aim of the project

It is the purpose of this project to show the usefulness of the systematic design method and extend the method. With the advent of new (largely digital) signal processing techniques, the requirements on analog IF/HF building blocks are likely to change. Furthermore, the downscaling of CMOS processes leads to lower supply voltages, while power consumption is also a very important design issue. In view of all these trends, the availability of a large arsenal of alternative circuit topologies is likely to be very useful. However, generating a large set of topologies is not enough! A sizing strategy is needed to design the circuits in such a way as to satisfy a set of specifications. Furthermore, a method for fair comparison of alternative circuits is needed, to select the best performing circuit. These problems will be addressed in the currently proposed research project. Attention will be paid to:

  • Systematic generation of alternative circuit topologies for linear IF/HF circuits. Typical examples of circuits that can be designed using the method are broadband-amplifiers, AGC-amplifiers, Buffers, Transconductors and Trans-impedance amplifiers.
  • The development of a sizing strategy (choosing component values) to establish correct DC-biasing in circuits and/or satisfy a given set of design requirements. Hierarchical symbolic macro-models, developed in [12], will be used for first-cut design. Furthermore, as large numbers of circuits are involved, use will be made of automatic circuit optimisation tools.
  • The extension of existing behavioural macro-models to include important MOS-device properties like the finite output resistance, the back-gate effect and capacitive effects.
  • The validation of the design method and modelling by design experiments.

It is expected that the project will render results in two main fields:

  • Systematic design methodology, which is useful for design automation and education.
  • High-performance circuits.

Scientific Relevance

Several aspects make this project interesting from a scientific point of view:

  • The knowledge on HF CMOS circuits in the "Analog Circuits and Systems" group of MESA at Twente will be enhanced. It is expected that the trend to more and more digital signal processing will push the application area of analog signal processing to higher frequencies. Therefore, it is the aim of the group to extent the research in HF CMOS circuits (new assistant professor position Klumperink).
  • The state-of-the-art of analogue design methodology will be advanced. This is important for the research in the field of analogue CAD tools and the education of students in electronics (systematic design methodologies can be taught).
  • It is expected that the systematic topology generation will lead to new circuit topologies with improved performance.

Relevant Publication

[1] E.A.M. Klumperink, E. v.d.Zwan, E. Seevinck, "CMOS linear transconductor circuit with constant Bandwidth", Electronics Letters, Vol.25, No.10, pp. 675-676, May 1989.

[2] E. A. M. Klumperink and E. Seevinck, "MOS current gain cells with electronically variable gain and constant bandwidth", IEEE Journal of Solid-State Circuits, Vol. 24, No. 5, pp. 1465-1467, October 1989.

[3] E. A. M. Klumperink and H. J. Janssen, "Complementary CMOS current gain cell", Electronics Letters, Vol. 27, No. 1, pp. 38-39, January 1991.

[4] E. A. M. Klumperink, "Gate-drain Capacitance Compensation Technique for Triode MOS Transconductors", Electronics Letters, Vol. 27, No.2, pp. 113-115, Januari 1991.

[5] E. J. van der Zwan, E. A. M. Klumperink, and E. Seevinck, "A CMOS OTA for HF filters with programmable transfer function", IEEE Journal of Solid-State Circuits, Vol. 26, No. 11, pp. 1720-1724, November 1991.

[6] B. Nauta, E. A. M. Klumperink, and W. Kruiskamp, "A CMOS triode transconductor", Proceedings of the ISCAS '91, pp. 2232-2235, June 1991.

[7] E. A. M. Klumperink, "Cascadable CMOS current gain cell with gain insensitive phase shift", Electronics Letters, Vol. 29, No. 23, pp. 2027-2028, November 1993.

[8] E.A.M.Klumperink, C.H.J. Mensink, P. M. Stroet, Comment on "Low-voltage CMOS transductance cell based on parallel operation of triode and saturation transconductors", Electronics Letters, 30, pp. 1824-1825, 1994.

[9] E. A. M. Klumperink, C.T. Klein, B. Rüggeberg, A. J. M. v. Tuijl, "AM Suppression with low AM-PM conversion with the aid of a variable-gain Amplifier", IEEE Journal of Solid-State Circuits, Vol. 31, No. 5, pp. 625-633, May 1996.

[10] C. H. J. Mensink, E. A. M. Klumperink, B. Nauta, "On the Reduction of the Third Order Distortion in a CMOS Triode Transconductor", 1996 IEEE International Symposium on Circuits and Systems, Vol. 1, pg. 223-226, 1996.

[11] M. W. Hauser, E. A. M. Klumperink, R. G. Meyer, W. D. Mack, "Variable-Gain, Variable-Transconductance, and Multiplication Techniques: A Survey", In W. Sansen et al, editors, Analog Circuit Design, Dordrecht: Kluwer Academic Publishers, 1997.

[12] E.A.M. Klumperink, "Transconductance Based CMOS Circuits: Circuit Generation, Classification and Analysis", Ph.D. Thesis, University of Twente, The Netherlands, 1997.

[13] E. A. M. Klumperink, "A Systematic Approach to MOST Circuit Design and Analysis: Classification of 2VCCS Circuits", Proceedings of the 1997 European Conference on Circuit Theory and Design, Budapest, Hungary, pp. 1418-1423, September 1997.

[14] M. A. T. Sanduleanu, E. van Tuijl, E. A. M. Klumperink, R. Wassenaar, "CMOS Low Voltage Large Swing Transconductor", Proceedings of the 1997 European Conference on Circuit Theory and Design, Budapest, Hungary, pp. 1412-1417, September 1997.

Patents

[15] E. A. M. Klumperink, E. Seevinck, "Linear-gain amplifier arangement"; Patent Application Numbers: 8802631 (The Netherlands, October 26, 1988); 78102418 (Taiwan, March 28, 1989); 418414 (USA, October 6, 1989).


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