Microwave triodes

The valves treated in the paper are triodes with plane electrodes intended to be used as amplifier valves, local oscillators and transmitting valves in repeaters working in the super-high-frequency region. The most important factor in their design is the product of power gain and bandwidth. It is shown that this product is chiefly determined by valve parameters. For a high value of the gain-bandwidth product a high current density and a small cathode-grid distance are needed, resulting in a small electron transit time. A transit time of 1.3 × 10¿10 sec has been obtained. Although the deviations of input conductance and transadmittance from their d.c. values¿due to transit-time effects¿are considerable, these deviations have only a small influence on the gain-bandwidth product. A Table is given showing constructional and electrical data for a number of microwave triodes, of which one is in production. The others are in the experimental stage of development. The paper discusses the following properties of an amplifier with a microwave triode: (a) Gain-bandwidth product, 2Gc/s. (b) Noise figure, 16dB. (c) Variation of group-delay, 0.06 microsec. (d) Amplitude-phase conversion, 0.8 deg/dB. The figures mentioned are obtained with an amplifier stage equipped with an EC 57, a triode for operation at 4Gc/s.