FIG. 2: Carbon nanotube transistor characteristics including the DC current (inset) and the RF transconductance g RF m measured in the 0 − 0 . 8 GHz band (main panel) as function of gate voltage V$_{g}$ for a representative set of (color encoded) bias voltages increasing according to the arrow. The transconductance maximum for V$_{g}$ ≃ +0 . 5 V saturates at a large value ≳ 30 µ S. Low bias data, for V$_{d}$ = − (100 , 200 , 300) mV, are fitted with Eq.(2) (solid lines) within a prefactor ≃ 0 . 6 added to account for non ideal ballistic transport above the barrier. The fitting parameter, V$_{Te}$ = k$_{B}$T$_{e}$/eβ ≃ (120 , 140 , 170) ± 0 . 01 mV, gives (with β = 0 . 2) the thermal energies k$_{B}$T$_{e}$ = (24 , 28 , 34) meV. 9