A study of thermal chemical vapor deposition (CVD) grown carbon nanotubes (CNTs) field emitters in a triode amplifier configuration is reported. The CNT transistor characteristics were examined by integrating gate and anode with CNT cathode in two structural forms, utilizing a TEM grid (transmission electron microscope specimen holder) as the gate electrode and a micropatterned CNT with self-aligned gate. The TEM-grid CNT triode displayed clearly gate-controlled current modulation behavior with distinct cutoff, linear, and saturation regions, and a reasonable gate turn-on field of similar to 5.4 V/mu m despite a large cathode-gate spacing of similar to 120 mu m. The field emission result established the basic transistor characteristics of CNTs in a triode configuration. A CNT triode construct with a self-aligned gated fabrication technique was also developed to realize a monolithic triode structure with shorter gate-cathode spacing, lowering gate voltage, and enhancing emission current. The triode exhibited a significantly lower gate turn-on voltage of similar to 40 V, and gate-controlled modulation of the emission current. An anode current density of similar to 30 mA/cm(2) was achieved at a gate voltage of similar to 80 V and an anode voltage of similar to 200 V. The dc characteristics for both of the CNT triodes were investigated, including I-a versus V-a for different V-g. Moreover, dc parameters such as transconductance, amplification factors, and anode resistance of the triode amplifier were determined. The CNT triodes exhibited useful amplification factor and high output impedance. (c) 2005 American Vacuum Society.