High-performance experimental power triodes

The plate current, transconductance, gain-bandwidth product, and power output capabilities of small planar triodes have been increased nearly tenfold over that obtained from present day commercial tubes of comparable size and weight. In the new experimental triodes, the cathode can supply a CW current density of 1.6 A/cm². A closely spaced, rigidly supported grid structure can provide a transconductance of 0.7 mho. The output capacitance is low enough to render a gain-bandwidth product of 22 Gc/s at 1.3 Gc/s. In this frequency range, the CW power output capability is 1 kW, and the pulsed power output capability in a 10-percent bandwidth circuit is 5 kW with 500 μs pulses at a duty factor of 0.07.