An investigation of the power characteristics and saturation mechanisms in HEMTs and MESFETs

A method for large-signal transistor analysis is presented. The method is based on the harmonic-balance approach but makes use of input data from measured S-parameters instead of DC or pulsed DC characteristics and a large-signal equivalent circuit with harmonic elements. The topology of this circuit is nearly identical to commonly used small-signal equivalent circuits; its application allows a detailed interpretation of the computed results, which are very precise due to the use of small-signal S-parameters. The large-signal model is applied to HEMTs and MESFETs. Their saturation mechanisms are investigated and the operational difference is discussed. The importance of including higher harmonic signal components in the large-signal analysis is also shown.<
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