Summary
International Symposium on Nonlinear Theory and its Applications
2005
Session Number:4-1-3
Session:
Number:4-1-3-3
Modeling of a Chaotic Third-order Log-domain Filter
Alon Ascoli, Paul Curran, Orla Feely,
pp.278-281
Publication Date:2005/10/18
Online ISSN:2188-5079
Summary:
Log-domain filters are generally regarded as externally-linear internally-nonlinear current-mode circuits, in which the large-signal forward-active mode exponential current-voltage relationship of the bipolar junction transistor is used to map the input currents to the logarithmic domain before any analog processing is carried out. The filtered voltages are then converted back to the linear domain using the exponential mapping once again. When a common integrated circuit design practice is applied to such internally-nonlinear circuits, the resulting filters lose external linearity. Transistor parasitics play a crucial role in the emergence of such externallynonlinear behavior. In this paper a transistor dynamic model is used to explain the chaotic behavior recently observed in a third-order log-domain filter for zero input.