Within the proposed four-year program, the goal is to reach transistor gain
cut-off frequencies in excess of one Terahertz, and circuit fundamental operating frequencies of 300 to 500 GHz, with useable output power in the range of a few milliwatts.
Thus, the resonator (or at least the tunable part of it), which is the lossy part, was completely separated from the active part, generating negative resistance using transistor gain
. The imaginary components of the active and passive part impedances indicate the oscillation point.
Based on Cree s proven 40V, 0.25 om gate length high frequency process, Cree GaN DFN transistors deliver twice the PSAT efficiency and transistor gain
of Gs IMFETs in a package size that is nearly 20 times smaller at comparable power levels and frequencies.
If the oscillator is operated with a low current, care must be taken that the transistor gain
[S.sub.21] is still sufficient.
Superimposed on the contours are the transistor gain
circles at the external load obtained from S-parameter measurements on the same device.