Cathodefollower Rf Power Amplifier
Showing the relationships between the tube potentials and currents and the input and output power of the stage. The approximate grid impedance also is given.
The design of such an amplifier stage is essentially the same as the design of a grounded-grid amplifier stage as far as the first step is concerned. Then, for the second step the operating conditions given in figure 10 are applied to the data obtained in the first step. As an example, take the 304TL stage previously described. The total power required of the driver will be (from figure 10) approximately (2700X0.58X1.8)/2 or 141 watts. Of this 141 watts 27.5 watts (as before) will be lost as grid dissipation and bias loss and the balance of 113.5 watts will appear as output. The total output of the stage will then be approximately 963 watts.
Cathode Tank for The cathode tank circuit G-GorC-F for either a grounded-grid
Power Amplifier or cathode-follower r-f power amplifier may be a conventional tank circuit if the filament transformer for the stage is of the low-capacitance high-voltage type. Conventional filament transformers, however, will not operate with the high values of r-f voltage present in such a circuit. If a conventional filament transformer is to be used the cathode tank coil may consist of two parallel heavy conductors (to carry the high filament current) by-passed at both the ground end and at the tube socket. The tuning capacitor is then placed between filament and ground. It is possible in certain cases to use two r-f chokes of special design to feed the filament current to the tubes, with a conventional tank circuit between filament and ground. Coaxial lines also may be used to serve both as cathode tank and filament feed to the tubes for v-h-f and u-h-f work.
Average user rating: 5 stars out of 1 votes
Post a comment