CMOS Comparators

  • Rafael Domínguez-Castro
  • Manuel Delgado-Restituto
  • Angel Rodríguez-Vázquez
  • José M. de la Rosa
  • Fernando Medeiro
Chapter

Abstract

Comparators are used to detect whether an analog signal x +(t) is larger or smaller than other x (t) †2, and to codify the outcome in digital domain as follows,
$$y=\left \{ \begin{matrix} 1_{\textup{D}}\;\;\;\;\;\;\;\textup{for}\;\;\;\;\;x_{+}(t)>x_{-}(t) \ 0_{\textup{D}}\;\;\;\;\;\;\;\textup{for}\;\;\;\;\;x_{+}(t)<x_{-}(t) \end{matrix} \right.$$
(4.1)
where y is the output signal, 0 D represents the logic zero and 1 D is the logic one. Ideal comparators should be capable to detect arbitrarily small differences between the input signals. However, in practice, these differences must be larger than a characteristic resolution parameter ξ for proper detection. For a given comparator circuit, the value of this resolution parameter changes depending upon the operating conditions. If the temporal window allocated for comparison is long enough, ξ takes an absolute minimum value which is inherent in the comparator device and which defines its maximum accuracy. As the temporal window shrinks, the value of ξ increases above its absolute minimum value and, hence, the comparator accuracy worsens. It highlights a trade-off between accuracy and speed of operation; the larger the speed the smaller the accuracy. As in any other analog circuit this trade-off is also influenced by power consumption and area occupation.

Keywords

Static Resolution Static Gain Stable Equilibrium Point Differential Input Reset Phase 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 2003

Authors and Affiliations

  • Rafael Domínguez-Castro
  • Manuel Delgado-Restituto
  • Angel Rodríguez-Vázquez
  • José M. de la Rosa
  • Fernando Medeiro

There are no affiliations available

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