. The thermionic vacuum tube and its applications . omes: 0 o This is also a maximum when Zq is numerically equal to Vp, as isshown in Fig. 112, page 220, where the curve represents the relation Z between the power amplification and the ratio — for the case in which angle of the external impedance Zq is 45°, that is,tan (i> = ~= 1. \\Tien the tube is used for the purpose of amplify-ing telephonic currents, the energy is translated into sound wavesthrough the motion of the receiver diaphragm. In such cases, THE THERMIONIC AMPLIFIER 189 Z it will be shown later, the ratio ~ can deviate consid
. The thermionic vacuum tube and its applications . omes: 0 o This is also a maximum when Zq is numerically equal to Vp, as isshown in Fig. 112, page 220, where the curve represents the relation Z between the power amplification and the ratio — for the case in which angle of the external impedance Zq is 45°, that is,tan (i> = ~= 1. \\Tien the tube is used for the purpose of amplify-ing telephonic currents, the energy is translated into sound wavesthrough the motion of the receiver diaphragm. In such cases, THE THERMIONIC AMPLIFIER 189 Z it will be shown later, the ratio ~ can deviate considerably from unity before resulting in any serious duninution of the effectproduced upon the organs of hearing. If we put ZQ=nrp equation (33) becomes: (jr Tg cos (j> (36) which clearly shows the importance of the mutual conductance - or the steepness of the plate current-grid voltage characteristic. It will be seen later that this quantity plays an equally importantrole in the operation of the tube as oscillation generator and i^.C. Input Fig. 93. 64. Experimental Verification of Amplification Squations. The amplification was determined experimentally as a functionof the tube parameters with the circuit arrangement shown inFig. 93.^ This circuit was made non-inductive input voltage could be varied by means of the resistance riand measured with a Duddell thermo-galvanometer Gi and resist-ance r2. The grid battery Eg was inserted to insure that the tubewas always operated within the limits given by equations (24).Now the amplifier is always operated with a batteiy in the platecircuit, so that there is a constant direct current in this circuitwhether the a-c. input be applied or not. The application of the 1 H. J. VAN DER BiJL, Phys. Rev., Vol. 12, p. 194, 1918. 190 THERMIONIC VACUUM TUBE a-c. input voltage establishes an alternating current in the platechcuit which is superhnposed upon the constant direct a-c. could not be measure
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