A complete Gallium Arsenide Metal Semiconconductor
Field Effect Transistor (GaAs MESFET) model including deep-level
trap effects has been developed, which is far more
accurate than previous equivalent circuit models, for high-speed
applications in linear integrated circuit design.
A new self-backgating GaAs MESFET model, which can
simulate low frequency anomalies, is presented by including
deep-level trap effects which cause transconductance
reduction and the output conductance and the saturation
drain current to increase with the applied signal frequency.
This model has been incorporated into PSPICE and includes a
time dependent I-V curve model, a capacitance model, a
subthreshold current model, an RC network describing the
effective substrate-induced capacitance and resistance, and
a switching resistance providing device symmetry.
An analytical approach is used to derive capacitances
which depend on Vgs and Vds and is one which also includes
the channel/substrate junction modulation by the self
backgating effect. A subthreshold current model is
analytically derived by the mobile charge density from the
parabolic potential distribution in the cut-off region. Sparameter
errors between previous models and measured data
in conventional GaAs MESFET's have been reduced by including
a transit time delay in the transconductances, gm and gds,
by the second order Bessel polynomial approximation. As a
convenient extraction method, a new circuit configuration is
also proposed for extracting simulated S-parameters which
accurately predict measured data. Also, a large-signal GaAs
MESFET model for performing nonlinear microwave circuit
simulations is described.
As a linear IC design vehicle for demonstrating the
utility of the model, a 3-stage GaAs operational amplifier
has been designed and also has been fabricated with results
of a 35 dB open-loop gain at high frequencies and a 4 GHz
gain bandwidth product by a conventional half micron MESFET
technology. Using this new model, the low frequency
anomalies of the GaAs amplifier such as a gain roll-off, a
phase notch, and an output current lag are more accurately
predicted than with any other previous model.
This new self-backgating GaAs MESFET model, which
provides accurate voltage dependent capacitances, frequency
dependent output conductance, and transit time delay
dependent transconductances, can be used to simulate low
frequency effects in GaAs linear integrated circuit design. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37482 |
| Date | 31 May 1990 |
| Creators | Lee, Mankoo |
| Contributors | Forbes, Leonard |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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