Extraction Algorithms

This section describes the extraction algorithms used for inductance, capacitance, DC, and series resistance parameters of the UCB GaAs MESFET.

Inductance and Resistance Extraction

Inductors and resistors that are in series with each terminal of the MESFET are measured with a network analyzer at a high frequency and with the gate strongly forward-biased. Under these conditions the AC model for each terminal is reduced to a series R-L circuit. Inductors LD, LG, and LS and resistors RD, RG, and RS are extracted simultaneously from the measured impedance at the gate and drain ports.

DC Parameter Extractions

DC extractions are separated between the diode and forward active controlling parameters. Diode parameters PB, IS, and XN are extracted using a method similar to the method used for a silicon diode. The diode is swept over a forward bias and linear least-squares curve fits will produce the built-in potential and forward conduction properties.

The forward active region is extracted from measurements of the MESFET in both the linear and saturated modes of operation. The difference between the equations defining these two regions is a tanh(ALPHA · Vds) multiplier in the linear mode. The threshold can be obtained from a least-squares fit to the linear region. These equations are solved to produce ALPHA, B, BETA, LAMDA, and VTO.

Capacitance Parameter Extractions

The capacitance of the gate-to-drain (CGD) and gate-to-source (CGS) is measured with S-parameters over typical operating frequencies. Because the inductances and series resistance are already known, these capacitances can be extracted from the corrected impedances measured at the gate and drain ports.