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Future Device
Modeling Trends
David E. Root




G
ood transistor models are essential for able to keep up. These and other challenges have spawned
efficient computer-aided-design (CAD) much research into the advanced nonlinear device
of nonlinear microwave and RF circuits, modeling techniques that are the focus of this article.
monolithic microwave integrated cir- The scope of this article is restricted to modeling the
cuits (MMICs), power amplifiers (PAs), nonlinear device for circuit and system simulation down-
and nonlinear RF systems. Increasingly complicated stream. "Device" means not only transistor but also diode
demands of the various semiconductor technologies (e.g., or other basic nonlinear component. For clarity and consis-
GaAs pHEMTs, InP double heterojunction bipolar tran- tency with common usage, the term "compact model" will
sistors (DHBTs), silicon on insulator (SOI), LDMOS, GaN be reserved for models defined by nonlinear equivalent
HFETs, etc.), and their applications in terms of power and circuits in the time domain, or, equivalently, by a system of
frequency of operation and complexity of applied signals nonlinear ordinary differential equations. Classically, com-
(e.g., modern communication signals with high peak-to- pact model also meant constitutive relations [current-volt-
average ratios) have placed commensurate requirements age (I-V) and charge-voltage (Q-V) relations for nonlinear
on the accuracy and generality of the device models lumped elements] defined by explicit closed-form expres-
used for design. New semiconductor material systems sions with parameter values specified by physics or extracted
(e.g., GaN) have been developing at such a fast rate that from measurements. An example is shown in Figure 1
conventional compact modeling approaches may not be for a generic field-effect transistor (FET) model. For this



David E. Root ([email protected]) is with Agilent Technologies, Inc., Santa Rosa, California 95403 USA.

Digital Object Identifier 10.1109/MMM.2012.2216095
Date of publication: 14 November 2012