Digital Integrated Circuit Design
Working from the fundamentals of transistor-level design and building up to system-level considerations, this text demonstrates how to design state-of-the-art high performance digital integrated circuits.
TABLE OF CONTENTS Digital Integrated Circuit Design
3.6: SPICE-Modeling Parameters
3.6 SPICE-Modeling Parameters
This section briefly describes some of the important model parameters for diodes, bipolar transistors, and MOS transistors, used during a SPICE simulation (Massobrio and Antognetti, 1993). Not all SPICE model parameters are described; however, enough are described to enable the reader to understand the relationship between the relative parameters and the corresponding constants used when doing hand analysis. This section is relevant to SPICE modeling where a physical relationship exists between the SPICE parameters and the actual transistor; some modern models that do not posses this feature (such as the Berkeley BSIM models) are beyond the scope of this text.
DIODE MODEL PARAMETERS
There are a number of important d.c. parameters. The constant I S is specified using either the parameter IS or JS in SPICE. These two parameters are synonyms for each other and only one should be specified. A typical value specified might be between 10 ?18 and 10 ?15 A for small diodes in a microcircuit. Another important parameter is called the emission coefficient, n. This constant multiplies V T in the exponential diode I-V relationship given by
The SPICE parameter for n is N and is defaulted to 1 when not specified (which is a reasonable value for junctions in a microcircuit). A third important d.c. characteristic is the series resistance, which is specified in SPICE using RS. Note that some SPICE programs allow the user to specify the...
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