Transistor critical sizing in MOBILE follower

Analyses are presented of how the presence of the HFET transistor modifies the DC operation of a resonant tunnelling logic follower MOBILE. The difficulty of an analytical study for the resulting circuit has been overcome by resorting to simplified descriptions for both the RTD and the HFET I-V characteristics. We have obtained an analytical expression for the relation of the ratio of gate width to the gate length of the HFET below which a theoretically well designed follower does not operate correctly.