. The Bell System technical journal . the fundamental of Ip are 180 out of THERMIONIC VACUUM TUBES 85 phase. This latter condition is obviously required for maximumpower output by an generator. In order that IP be a maximumwhen Ep is a minimum, Eg must be a maximum at this time. 47. Dynamic Characeristic. A tube when operating into an outputresistance follows a dynamic characteristic (also called derived char-acteristic)37 whose slope is somewhat less than that of the static (seeSec. 12). The dynamic characteristic is flatter than the static char-acteristic since the oscillating circuit L
. The Bell System technical journal . the fundamental of Ip are 180 out of THERMIONIC VACUUM TUBES 85 phase. This latter condition is obviously required for maximumpower output by an generator. In order that IP be a maximumwhen Ep is a minimum, Eg must be a maximum at this time. 47. Dynamic Characeristic. A tube when operating into an outputresistance follows a dynamic characteristic (also called derived char-acteristic)37 whose slope is somewhat less than that of the static (seeSec. 12). The dynamic characteristic is flatter than the static char-acteristic since the oscillating circuit Li, C acts as an equivalent re-sistance. In fact, the dynamic characteristic of the oscillating tubemay differ in one important respect from that of Sec. 12, for in anoscillator the grid potential has a relatively very high positive valuefor a portion of the cycle. Consequently the dynamic plate char-acteristic very frequently turns downward at its upper end (point B,Fig. 56). As will be pointed out later, this feature of the dynamic. Gnd Potential Fig. 56 characteristic is likely to be one of the factors tending to limit theamplitude of oscillation. 48. Amplitude of Oscillation. As yet no very comprehensiveformula has been derived, either theoretically or empirically, to expressthe amplitude of oscillation in terms of the tube and circuit constantsand the applied Ep. However, certain general statements can bemade which will serve as useful guides. We shall not consider further the circuit shown in Fig. 54; it showsa negative grid battery in the grid filament branch, which, if sufficientlylarge to control the oscillator when in operation, usually makes thestarting difficult and uncertain, and is therefore undesirable. Toeliminate the grid battery and yet supply sufficient negative potential,once oscillations have started, circuits are usually supplied with agrid blocking condenser and high resistance leak (see Figs. 64 and65). Since for a portion of each oscillation the grid is
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