Comparison of variable gain LNA MMICs at c-band using GaAs enhancement, depletion or deep-depletion MESFETs

Abstract

In this paper, the transmission phase variation, the noise figure and the large signal performance versus gain or cascode VGLNAs (variable gain low noise amplifiers) are compared, using either enhancement, depletion or deep-depletion MESFETs. To allow objective comparisons, the same circuit topology, bias current and bias voltage are used for the three C-band GaAs MMICs (microwave monolithic integrated circuits). The VGLNAs with depletion FETs are superior in terms of transmission phase constancy and large signal performance, whereas the VGLNA with enhancement FETs provides higher maximum gain and lower noise figure.