NQS - Non-Quasi Static model - is a transistor model used in analogue/mixed signal IC design. It becomes necessary to use an NQS model when the operational frequency of the device is in the range of its transit time. Normally, in a quasi-static (QS) model, voltage changes in the MOS transistor channel are assumed to be instantaneous. However, in an NQS model voltage changes relating to charge carriers are delayed.
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NQS Wikipedia(Text) CC BY-SA