An Efficient Large-Signal Modeling Method Using Load-Line Analysis and Its Application to Non-linear Characterization of FET

Kazutomi MORI
Masatoshi NAKAYAMA
Yasushi ITOH
Tadashi TAKAGI

IEICE TRANSACTIONS on Electronics   Vol.E84-C    No.7    pp.875-880
Publication Date: 2001/07/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Techniques for Constructing Microwave Simulators--Design and Analysis Tools for Electromagnetic Fields, Circuits, and Antennas--)
Category: Modeling of Nonlinear Microwave Circuits
microwave,  amplifier,  FET,  modeling,  nonlinear analysis,  

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An efficient large-signal modeling method of FET using load-line analysis is proposed, and it is applied to non-linear characterization of FET. In this method, instantaneous drain-source voltage Vds(t) and drain-source current Ids(t) waveforms are determined by load-line analysis while non-linear parameters in a large-signal equivalent circuit of FET are defined as the average values over one period corresponding to instantaneous Vds(t) and Ids(t). Output power (Pout), power added efficiency (ηadd), and phase deviation calculated by using such an equivalent circuit of FET agree well with the measured results at 933.5 MHz. Phase deviation mechanism is explained based on the large-signal equivalent circuit of FET, and it is shown how non-linear parameters, such as trans-conductance (gm), drain-source resistance (Rds), gate-source capacitance (Cgs), and gate leak resistance (Rig) contribute to positive or negative phase deviations. The difference between small-signal and large-signal S-parameters (S11, S12, S21, S22) is also discussed. The proposed large-signal modeling method is considered to be useful for the design of high power, high efficiency, and low distortion amplifiers as well as the investigation of the behavior of FET in large-signal operating conditions.