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PS JFET - MESFET Model

This comprehensive large-signal MESFET model provides a realistic description of measured characteristics over all operating regions. It describes subthreshold conduction and breakdown. It has frequency dispersion of both transconductance and drain conductance, and derates with power dissipation.

Its philosophy of strict mathematical continuity and realistic time-dependent behavior are proven by success with fast and accurate simulation of large-signal radio-frequency and communications circuits. All derivatives are continuous for a realistic description of circuit distortion and intermodulation. The model has improved descriptions of capacitance and bias dependence. It has small-signal S-parameter accuracy extended to a wide range of operating conditions. The model is implemented with new techniques for continuity and dispersion. These provide accurate prediction of circuit performance and also improve simulation speed.

Features

The model is a realistic description of measured characteristics over all operating regions. Its continuity permits correct prediction of distortion and intermodulation generation. Its rate and history dependence can simulate the looping observed on a curve tracer.

The PS model features characteristics that are essential for realistic simulation of large- and small-signal behavior with particular emphasis on distortion and frequency dispersion.

• The description maintains strict continuity in its high-order derivatives, which is essential for prediction of distortion and intermodulation.
• Frequency dependence of output conductance and transconductance is described as a function of bias.
• Both drain-gate and source-gate potentials modulate the pinch-off potential, which is consistent with S-parameter and pulsed-bias measurements.
• Self-heating varies with frequency.
• Extreme operating regions - subthreshold, forward gate bias, controlled resistance, and breakdown regions - are included.
• Parameters provide independent fitting to all operating regions. It is not necessary to compromise one region in favour of another.
• Strict drain-source symmetry is maintained. The transition during drain-source potential reversal is smooth and continuous.

Strict continuity ensures reliable and rapid convergence. Despite the complexity of behavior that it describes, the model is faster than other simple models.

The model provides an essential tool for the design of modern communications circuits, which use many devices in various operating modes.

Implementation

The code for UCB Spice is available via the CNERF this model is contained in a single file, SPICE page.

The PSmodel in also included in most major SPICE simulators, including WinSpice3, MWOffice, Pspice, Anacad's Eldo, NG-SPICE, WRSPICE, Silvaco, and Intusoft's IS-SPICE.

Reference

The PSmodel implementation in MWOffice is described in (psfet.pdf).

A. E. Parker, and D. J. Skellern, "A Realistic Large-signal MESFET Model for SPICE," IEEE Transactions on Microwave Theory and Techniques, vol. 45, no. 9, pp. 1563-1571, Sept. 1997. The Institute of Electrical and Electronics Engineers, Inc., New York, ISSN 0018-9480.

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