Designs at the logic level of abstraction, describe a digital circuit in terms of primitive logic functions such as or, and nor, etc., and allow for the nets interconnecting the logic functions to carry 0, 1, x and z values. At the analog-transistor level of modeling, we use an electronic model of the circuit elements and allow for analog values of voltages or currents to represent logic values on the interconnections.

The switch level of modeling provides a level of abstraction between the logic and analog-transistor levels of abstraction, describing the interconnection of transmission gates which are abstractions of individual mos and cmos transistors. The switch level transistors are modeled as being either on or off, conducting or not conducting. Further, the values carried by the interconnections are abstracted from the whole range of analog voltages or currents to a small number of discrete values. These values are referred to as signal strengths.


Full Strength NAND Gate Pull Strength Strong Drive Gate Type 


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© Springer Science+Business Media, LLC 2008

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