The Kink Phenomenon in the Transistor ${\rm S} _{22}$ : A Systematic and Numerical Approach

This letter provides a valuable technique for evaluating the size and the shape of the kink effect in S₂₂ for microwave transistors. Since this phenomenon can be detected as the appearance of a concave shape in Im(S₂₂) versus Re(S₂₂), the second derivative of such a function is exploited for defining a set of parameters to fully and systematically characterize it. The effectiveness of the developed technique is demonstrated by its application to quantify the increase of the kink effect with the gate periphery for 0.15 μm GaAs HEMTs.