Analog Integrated Circuits and Signal Processing

, Volume 50, Issue 1, pp 59–67

Linearity of bulk-controlled inverter ring VCO in weak and strong inversion


DOI: 10.1007/s10470-006-9370-4

Cite this article as:
Wismar, U., Wisland, D. & Andreani, P. Analog Integr Circ Sig Process (2007) 50: 59. doi:10.1007/s10470-006-9370-4


In this paper linearity of frequency modulation in voltage controlled inverter ring oscillators for non feedback sigma delta converter applications is studied. The linearity is studied through theoretical models of the oscillator operating at supply voltages above and below the threshold voltage of a transistor, bringing the transistors in respectively strong and weak inversion. The theoretical results are tested with more advanced models through spectreRF simulations. A soft rail approach implemented to improve linearity in weak inversion is proposed and demonstrated. The influence from voltage noise, process variations and temperature variations have also been simulated to indicate the advantages of having the soft rail bias transistor in the VCO.


Inverter ringLinear modulationWeak inversionVCOFDSM

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© Springer Science + Business Media, LLC 2006

Authors and Affiliations

  1. 1.Centre for Physical Electronics, Ørsted·DTUTechnical University of DenmarkKgs. LyngbyDenmark
  2. 2.Microelectronic Systems, Department of InformaticsUniversity of OsloOsloNorway