. The thermionic vacuum tube and its applications . he fundamental phenomena of such main condition is that the plate current and grid potentialmust be as nearly in phase as possible. The phase relationfc be-tween the various quantities are shown in Fig. 157 and can beexplained with reference to Fig. 152. lb represents the steady direct current supplied by the batteiyEb thi-ough the choke coil. We can regard this current as constant, 1 L. A. Hazeltine, , Vol. 6, p. G3, 1918. 2 R. A. Heising, Journal of , Vol. 39, p. 365, 1920. VACUUM TUBE AS AN OSCILLATION GENERATOR
. The thermionic vacuum tube and its applications . he fundamental phenomena of such main condition is that the plate current and grid potentialmust be as nearly in phase as possible. The phase relationfc be-tween the various quantities are shown in Fig. 157 and can beexplained with reference to Fig. 152. lb represents the steady direct current supplied by the batteiyEb thi-ough the choke coil. We can regard this current as constant, 1 L. A. Hazeltine, , Vol. 6, p. G3, 1918. 2 R. A. Heising, Journal of , Vol. 39, p. 365, 1920. VACUUM TUBE AS AN OSCILLATION GENERATOR 281 although in actual practice it is only approximately so unless thechoke coil has a very large inductance. Ip represents the instan-taneous value of the plate current and I the instantaneous value ofthe current in the branch containing C and L2 in parallel. Thiscurrent multiplied by the instantaneous plate-filament voltageand integrated over a complete cycle, represents the a-c. powersuppUed by the tube. As much power is drawn from tlu^ tube as. Grid Pofenhal Anode Current Anode Po-henha/ Oufpuf Current Fig. 157. is dissipated in the oscillation cucuit when the steady conditionis reached. Referring to Fig. 157, the lines marked 0 represent the ordinatesof zero voltages and currents. The grid is maintained at a nega-tive potential Ec. When the alternating grid potential is zero,the plate current is equal to /&. When the grid potential oscillates,as indicated, the plate current oscillates in phase with thegrid potential. The plate potential oscillates around the meanvalue jEft, but is 180° out of phase with the grid potential if the 282 THERMIONIC VACUUM TUBE external circuit is non-reactive. The current I in the branch cir-cuit is the difference between direct current /& drawn from thebattery and the plate current 7p. It is therefore 180° out ofphase with the plate current and oscillates around zero. We haveassumed that the grid always remains negative with respect tothe ne
Size: 1233px × 2025px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookidthermionicva, bookyear1920
