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Reactors - Circuit Theory and Silicon Integrated Applications

Publiceringsår: 1999
Språk: Engelska
Dokumenttyp: Doktorsavhandling
Förlag: P. Andreani, P.O. Box 110, SE-221 00 Lund, Sweden


This dissertation deals with reactive components in electric circuits, both as targets for a theoretical circuit analysis, and as devices implemented in silicon processes like CMOS.

The frequency behavior of a general electric network is determined by the reactances (i.e., inductances and capacitances) present in the network, either as intentional parts of the design, or as process and implementation dependent parasitic phenomena. In either case, it is valuable to be able to investigate, with as little effort as possible, the influence of reactances on the transfer function of the network. With this in mind, the scope of the Cochrun-Grabel method for the analysis of circuits containing reactances has been extended to encompass a general RLC circuit containing mutual inductances. Furthermore, the method can now be applied to find also the numerator of the transfer function of a circuit, via a straightforward modification of the circuit under study.

Much attention has been paid to the use of the MOS structure as a monolithic capacitor, owing to two of its characteristics: the high capacitance per unit area, and the possibility to vary the capacitance value by changing the voltage between gate and bulk of an MOS transistor. A CMOS delay line with very high maximum speed was designed, where the delay was controlled through a bank of binary sized nMOS capacitors. One of the most exacting tasks in a standard CMOS process is the implementation of high performance radio frequency voltage controlled oscillators (VCOs), as they require both capacitors and inductors with very low losses. The behavior of an MOS capacitor employed as a variable reactor (varactor) was investigated in combination with both high quality bond wire inductors, and lower quality monolithic spiral inductors. These attempts show that the MOS varactor is likely to be a better choice than the commonly used reverse biased diode varactor in a deep sub-micron standard CMOS technology.

At frequencies below radio frequencies, inductive impedances are often mimicked with active gyrator circuits, made of capacitors and transconductors. If the active inductance is to be used in a bandpass filter, gyrating an LC-pair instead of the inductance alone may result in a filter architecture insensitive to parasitic capacitances, which greatly enlarges the operating frequency range of the filter.

The discrepancies between simulations and measurement results of both VCOs and bandpass filter stress the need for more accurate simulation models, able to capture the non-quasi-static behavior of the MOS transistor for signal frequencies close to the transit frequency of the device.


Hörsal E:1406, E-huset, Lund Tekniska Högskola
  • Bram Nauta (Prof)


  • Electrical Engineering, Electronic Engineering, Information Engineering
  • Active Filters
  • Delay Lines
  • VCOs
  • Inductors
  • Circuit Theory
  • Capacitors
  • CMOS
  • Electronics
  • Elektronik


  • ISSN: 1402-8662

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