Reinvestigation and extension of the steady-state Nyquist theorem for multi-terminal semiconductor devices and its application to minimum noise figure in microwave field effect transistors

Abstract

The steady-state Nyquist theorem for multi-terminal semiconductor devices, which describes the short-circuit thermal noise currents in arbitrarily shaped multi-terminal semiconductor devices, is reinvestigated. The concept of the equipotential surfaces for small ac signals is found to be wrong, which forces us to introduce a new approach to find the equipotential surfaces for noise voltages. Using this new approach, we rederive the steady-state Nyquist theorem with the same results as in the previous derivation, and extend it to the hot carrier regime. Using the extended theorem, we express the minimum noise figure for microwave field effect transistors as a function of the measurable device parameters with no fitting constant. The derived minimum noise figure is shown to reduce to a simple form, which can also be used as an empirical relation with one fitting constant. This simple form can explain the experimental results very well in wide frequency ranges, and gives through a clear mathematical relation the empirically known requirements for the low noise design of microwave field effect transistors.